1CVS 445: WATER RESOURCS ENGINEERING 1

Assessment: Course work 30% Final examination 70%

Course work schedule:CAT I:24/02/2005CAT II: 31/04/2005Course Assignments: 17 /02/2005 submit on 10/03/2005

COURSE OUTLINE

1. Definition of Integrated Water Resources Management and development (IWRD/M)2. Why Integrated Water Resources Management3. Dublin principles4. Water users and implication of change5. Integrated sustainable development in Water Resources engineering (WRE) process of

change6. Water interaction and balance7. Catchments based planning /management8. Legal & institutional framework and international obligation for IWRM9. Kenya in focus, National water campaign, Water ACT 200210. Introduction to WRE

2INTEGRATED WATER RESOURCES MANAGEMENT

Introduction to Integrated Water Resources Management (IWRM/D)Challenges faced by more and more countries in their struggle for economic and socialdevelopment are increasingly related to water. Water shortages, quality deterioration and floodimpacts are among the problems, which require greater attention and action. These concerns aregiving credence to the concept of Integrated Water Resources Management (IWRM) as a processto deal with water issues in a cost effective and sustainable way. But what does integrated waterresources management mean? Why is it so important? What are we losing without it? What arethe gains to be made from introducing it? If it is so good, why isnt everybody doing it already?

What is Integrated Water Resources Management (IWRM)IWRM has neither been unambiguously defined nor has the question of how it is to beimplemented been fully addressed. However, we can define Integrated Water ResourcesManagement (IWRM) as a participatory planning and implementation process, based on soundscience, to determine how to meet society's long-term needs for water resources whilemaintaining essential ecological services and economic benefits. In other words, it is a process,which promotes the coordinated development and management of water, land and relatedresources in order to maximize the resultant economic and social welfare in an equitable mannerwithout compromising the sustainability of vital ecosystems.IWRM helps to protect the worlds environment, foster economic growth and sustainableagricultural development, promote democratic participation in governance, and improve humanhealth. Worldwide, water policy and management are beginning to reflect the fundamentallyinterconnected nature of hydrological resources, and integrated water resources management isemerging as an accepted alternative to the sector-by-sector, top-down management style thathas dominated in the past.

In light of the foregoing a few points can be raised with respect to IWRM;

The basis of Integrated Water resources Management (IWRM) is that different usesof water are interdependent, hence the need to consider the different uses of watertogether. Integrated water resources management is a systematic process for the sustainabledevelopment, allocation and monitoring of water resource use in the context of social,economic and environmental objectives. At its simplest, integrated water resourcesmanagement is a logical and intuitively appealing concept. Its basis is that the many differentuses of finite water resources are interdependent. That is evident to us all. High irrigationdemands and polluted drainage flows from agriculture mean less freshwater for drinking orindustrial use; contaminated municipal and industrial wastewater pollutes rivers and threatensecosystems; if water has to be left in a river to protect fisheries and ecosystems, less can bediverted to grow crops. There are plenty more examples of the basic theme that unregulateduse of scarce water resources is wasteful and inherently unsustainable

Integrated management means that all the different uses of water resources areconsidered togetherWater allocations and management decisions consider the effects of each use on the others.They are able to take account of overall social and economic goals, including the achievementof sustainable development.

IWRM & participatory decision makingThe basic IWRM concept has been extended to incorporate participatory decision-making.Different user groups (farmers, communities, environmentalists) can influence strategies forwater resource development and management. That brings additional benefits, as informedusers apply local self-regulation in relation to issues such as water conservation and

3catchments protection far more effectively than central regulation and surveillance canachieve.

Deliberate management of resources is needed to ensure long-term sustainableuse...

Management is used in its broadest sense. It emphasises that we must not only focus ondevelopment of water resources but that we must consciously manage water developmentin a way that ensures long term sustainable use for future generations.

IWRM is a systematic processIntegrated water resources management is a systematic process for the sustainabledevelopment, allocation and monitoring of water resource use in the context of social,economic and environmental objectives. It is different from the sectoral approach appliedin many countries...When responsibility for drinking water rests with one agency, that of irrigation water witha different one and responsibility for the environment with yet another, there result lack ofcross-sectoral linkages leading to uncoordinated water resource development andmanagement, resulting in conflict, waste and unsustainable systems.

WHY IWRM?

The Facts:

Of the Global water sources, 97% is seawater, and 3% is freshwater. Of the freshwater87% is not accessible, meaning only 13% of freshwater is accessible, a mere 0.4% ofthe total!

Today more than 2 billion people are affected by water shortages in over 40 countries. 263 river basins are shared by two or more nations; 2 million tonnes per day of human waste are deposited in water courses Half the population of the developing world are exposed to polluted sources of water that

increase disease incidence. 90% of natural disasters in the 1990s were water related.

It is evident that the worlds freshwater resources are under increasing pressure, and the increasein numbers of people from 6 billion to 9 billion will be the main driver of water resourcesmanagement for the next 50 years. Hence IWRM is driven by the recognition of water as vital forhuman survival, health and dignity and a fundamental resource for human development.

Growth in population, increased economic activity and improved standards of living lead toincreased competition for and conflicts over the limited freshwater resource. A combination ofsocial inequity and economic marginalisation forces people living in extreme poverty lead tooverexploit of soil and forestry resources, with damaging impacts on water resources.Here are a few reasons why many people argue that the world faces an impending water crisis:

Water resources are increasingly under pressure from population growth, economicactivity and intensifying competition for the water among users;

Water withdrawals have increased more than twice as fast as population growth andcurrently one third of the world's population live in countries that experience medium tohigh water stress;

Pollution is further enhancing water scarcity by reducing water usability downstream; Shortcomings in the management of water, a focus on developing new sources rather than

managing existing ones better, and top-down sector approaches to water managementresult in uncoordinated development and management of the resource;

4 More and more development means greater impacts on the environment; Current concerns about climate variability and climate change demand improved

management of water resources to cope with more intense floods and droughts.

PRINCIPAL COMPONENTS OF IWRM

Managing water resources at the basin or watershed scale. This includes integratingland and water, upstream and downstream, groundwater, surface water, and coastalresources.

Optimising supply. This involves conducting assessments of surface and groundwatersupplies, analysing water balances, adopting wastewater reuse, and evaluating theenvironmental impacts of distribution and use options.

Managing demand. This includes adopting cost recovery policies, utilizing water-efficienttechnologies, and establishing decentralized water management authorities.

Providing equitable access to water resources through participatory and transparentgovernance and management. This may include support for effective water usersassociations, involvement of marginalized groups, and consideration of gender issues.

Establishing improved and integrated policy, regulatory, and institutionalframeworks. Examples are implementation of the polluter-pays principle, water qualitynorms and standards, and market-based regulatory mechanisms.

Utilizing an intersectoral approach to decision-making, where authority formanaging water resources is employed responsibly and stakeholders have a share in theprocess.

Water management PrinciplesA meeting in Dublin in 1992 (The International Conference on Water and Environment, Dublin,Ireland, January 1992.) gave rise to four principles that have been the basis for much of thesubsequent water sector reform.

Fresh water is a finite and vulnerable resource, essential to sustain life, development and theenvironment

Water development and management should be based on a participatory approach, involvingusers, planners and policymakers at all levels.

Women play a central part in the provision, management and safeguarding of water. Water has an economic value in all its competing uses and should be recognised as an

economic good

i. Fresh water is a finite and vulnerable resource, essential to sustain life, development andthe environment.

Since water sustains life, effective management of water resources demands a holistic approach,linking social and economic development with protection of natural ecosystems. Effectivemanagement links land and water uses across the whole of a catchment area or groundwateraquifer.The notion that freshwater is a finite resource arises as the hydrological cycle on average yields afixed quantity of water per time period. This overall quantity cannot yet be altered significantly byhuman actions, though it can be, and frequently is, depleted by man-made pollution. Thefreshwater resource is a natural asset that needs to be maintained to ensure that the desiredservices it provides are sustained. This principle recognises that water is required for manydifferent purposes, functions and services; management therefore, has to be holistic (integrated)and involve consideration of the demands placed on the resource and the threats to it.The integrated approach to management of water resources necessitates co-ordination of therange of human activities, which create the demands for water, determine land uses and generate

5waterborne waste products. The principle also recognises the catchment area or river basin as thelogical unit for water resources management.

ii. Water development and management should be based on a participatory approach,involving users, planners and policymakers at all levels.

The participatory approach involves raising awareness of the importance of water among policy-makers and the general public. It means that decisions are taken at the lowest appropriate level,with full public consultation and involvement of users in the planning and implementation of waterprojects.Water is a subject in which everyone is a stakeholder. Real participation only takes place whenstakeholders are part of the decision-making process. The type of participation will depend uponthe spatial scale relevant to particular water management and investment decisions. It will beaffected too by the nature of the political environment in which such decisions take place.A participatory approach is the best means for achieving long-lasting consensus and commonagreement. Participation is about taking responsibility, recognizing the effect of sectoral actionson other water users and aquatic ecosystems and accepting the need for change to improve theefficiency of water use and allow the sustainable development of the resource. Participation doesnot always achieve consensus, arbitration processes or other conflict resolution mechanisms alsoneed to be put in place. Governments have to help create the opportunity and capacity toparticipate, particularly among women and other marginalised social groups. It has to berecognised that simply creating participatory opportunities will do nothing for currentlydisadvantaged groups unless their capacity to participate is enhanced.

iii. Women play a central part in the provision, management and safeguarding of waterThis pivotal role of women as providers and users of water and guardians of the livingenvironment has seldom been reflected in institutional arrangements for the development andmanagement of water resources.Acceptance and implementation of this principle requires positive policies to address womensspecific needs and to equip and empower women to participate at all levels in water resourcesprogrammes, including decision-making and implementation, in ways defined by them.It is widely acknowledged that women play a key role in the collection and safeguarding of waterfor domestic and in many cases agricultural use, but that they have a much less influentialrole than men in management, problem analysis and the decision-making processes related towater resources. The fact that social and cultural circumstances vary between societies suggeststhat the need exists to explore different mechanisms for increasing womens access to decision-making and widening the spectrum of activities through which women can participate in IWRM.IWRM requires gender awareness. In developing the full and effective participation of women atall levels of decision-making, consideration has to be given to the way different societies assignparticular social, economic and cultural roles to men and women. There is an important synergybetween gender equity and sustainable water management. Involving men and women ininfluential roles at all levels of water management can speed up the achievement ofsustainability; and managing water in an integrated and sustainable way contributes significantlyto gender equity by improving the access of women and men to water and water-related servicesto meet their essential needs.

iv. Water has an economic value in all its competing uses and should be recognised as aneconomic good.

Within this principle, it is vital to recognise first the basic right of all human beings to have accessto clean water and sanitation at an affordable price. Yet Water has a value as an economic goodas well as a social good. Many past failures in water resources management are attributable tothe fact that the full value of water has not been recognised and has led to wasteful andenvironmentally damaging uses of the resource.Treating water as an economic good is an important means for decision making on the allocationof water. This is particularly important when extending supply is no longer a feasible option.

6Water has a value as an economic good as well as a social good. Many past failures in waterresources management are attributable to the fact that the full value of water has not beenrecognised. In order to extract maximum benefits from available water resources, there is a needto change perceptions about the value of water.Value and charges are two different things and we have to distinguish clearly between valuingand charging for water.The value of water in alternative uses is important for the rational allocation of water as a scarceresource, whether by regulatory or economic means.Charging (or not charging) for water is applying an economic instrument to supportdisadvantaged groups, affect behaviour towards conservation and efficient water usage, provideincentives for demand management, ensure cost recovery and signal consumers willingness topay for additional investments in water services.Treating water as an economic good is an important means for decision making on the allocationof water between different water use sectors and between different uses within a sector. This isparticularly important when extending supply is no longer a feasible option.In IWRM, economic valuation of alternative water uses gives decision makers important guides toinvestment priorities. It should not though be the only consideration. Social goals are importanttoo. In a water-scarce environment, would it be right, for example, that the next water resourcedeveloped should be assigned to a steel-manufacturing plant because the manufacturer canafford to pay more for the water than the thousands of poor people who have no access to safewater? Social, economic and environmental goals all play a part in IWRM decision-making.

7PROCESS OF IMPLEMENTING IWRMThe overall objective of IWRM is to lay the foundation for rational and efficient framework formeeting the water needs for development, social and environmental uses. The strategyencompasses institutional reforms that separate the functions of;

Water service delivery, Management and administration Policy and regulation

The process of implementing IWRM is really a challenge to conventional practices. The case forIWRM is strong indeed incontestable, but the problem in most countries is the long history of uni-sectoral development. In this respect IWRM is a challenge to convectional practices, attitudes andprofessional certainties. It confronts entrenched sectoral interests and requires that the waterresource be managed holistically for the benefits of all.

All this implies change, which brings threats as well as opportunities. There are threats to peoplepower and position; and threat to their sense of themselves as professionals. IWRM require thatplatform be developed to allow different interest groups top negotiate their differences andsomehow nonetheless work together.

IWRM requires reforms and obviously on step-by-step basis, where some changes take placeimmediately and others needing several years of planning and implementation.

Integrated water resources management is as concerned with water demand as with its supply.Thus integration can be considered as integration of natural systems with its vital role of resourceavailability and quality and human systems, which fundamentally determines the resource use,waste production, and pollution of the resource. Traditionally, water managers viewed their roleas that of meeting demand that is externally determined. IWRM approaches should assist inshaping demand e.g. in terms of quality, availability, peak demand.

The process of integrated water resourced management involves integration of variousmanagement aspects namely;

Integration of Land and water managementAn integrated land and water management is d departure form the hydrological cycle oftransporting water between compartments air, soil, vegetation, surface and groundwater sources.As a result, land use developments and vegetation cover influence the physical distribution andquality of water and must be considered in the overall planning and management of the waterresources. This integration process also takes into account the water is a key determinant of boththe terrestrial and aquatic ecology. Catchment and basin level management is not only importantas a means of integrating land use and water issues, but is also critical in managing therelationships between quantity and quality and between upstream and downstream waterinterests.

Integration of quality and quantity in water resources managementWater resources management entails the development of appropriate quantities of water with anadequate quality. Water quality management is thus an essential component of IWRM. Thedeterioration of water quality reduces the usability of the resource for downstream users. Clearly,institutions capable of integrating the quantity and quality aspects have to be promoted toinfluence the way human systems operate in generating, abating and disposing of wasteproducts.

Integration of surface and groundwater managementThe hydrological cycle calls for integration between surface and groundwater management. Thedrop of water retained at the surface of a catchment may appear alternately as surface and

8ground water on its way downstream through the catchment. Large sections of the worldpopulation depend on groundwater.

Integration of cross-sectoral and upstream downstream dialogueA critically important role of IWRM is the integration of various sectoral views and interest in thedecision making process, with due alternatives given to upstream downstream relationships.The consumptive losses upstream will reduce river flows. The pollution loads dischargedupstream will degrade river water quality. Land use changes upstream may alter groundwaterrecharge and river flow seasonality. Flood control measures upstream may threaten flood dependent downstream such conflicts of interest must be considered in IWRM with fullacknowledgement of range of physical and social linkages that exist in complex systems.Recognition of downstream vulnerability to upstream activities is imperative

Integration of Freshwater and coastal zone managementFreshwater and coastal zone management should be integrated, reflecting the inter-relationshipbetween the two. Freshwater systems are important determinants of conditions in the coastalzone and hence freshwater managers should consider the requirements of the coastal zone whenmanaging water resources. This is a special case of the upstream-downstream issue, which isreceiving increased attention

Integrating water and wastewater managementWater is renewable and reusable resources. Where use is non-consumptive and returned afteruse, mechanisms are needed to ensure that wastewater flows are useful addition to resourceflows or water supply. Without co-ordinated management, waste flows often simply reduceeffective supplies by impairing water quality and increasing future costs of water supply.Incentives for reuse can be provided to individual user but to be effective reuse opportunitieshave to be designed into the political, economic, social and administrative systems.

In a nutshell the process of IWRM needs to recognise and pursue social, economic and naturalconditions:Economic efficiency in water use: water must be used to maximise efficiency with mind thescarcity of water and financial resources, the finite and vulnerable natures of water resources,and increasing demand upon it.

Equity: basic right of all people to have access to water of adequate quantity and quality forsustenance must always be safeguarded

Environmental and ecological sustainability: Present use of water must not be managed in away that will undermine the life support system thereby compromising future users of water.

Water users Agriculture Water supply & wastewater Mining, industry Environment Fisheries Tourism Energy Transport

Each of the water uses identified above has valuable positive and negative impacts.Negative impacts which may be made worse by poor management practices

9PrioritiesEach country has its priority developmental and economic goals set according to environmental,social and political realities.

Social and economic benefits from water use sectors.These are generally obvious in terms of food production, energy production, drinking water, jobs,recreation, etc, but the relative value of these benefits is more difficult to assess

Prioritising allocation between sectors...When there is competition for water resources it brings into the open the need to justify theallocation of water to one user rather than to another. This value assessment should take intoaccount both the benefits and the negative impacts. The input from users, politicians and societyin general is necessary as the allocation may not be most efficient when valued in economic termsalone or acceptable when made only on political grounds

ENVIRONMENT Maintenance of functioning of ecosystems

Terrestrial and aquatic ecosystems need water to maintain their functioning: plants evaporate andtranspire water; animals drink water; fish and amphibians need water to live in. Water is alsoused by upper-watershed ecosystems, downstream, wetlands, floodplains, and mangroves needfreshwater inputs. This water is used to maintain a (semi)-natural dynamic, often of a seasonalnature. To prevent degradation and destruction of ecosystems, it is important to have enoughwater of the right quality and with the right seasonal variability.

Loss of environmental maintenance in return means the loss of free environmental benefits fuelwood, water, fisheries, fruits. They can also contribute to ecosystem degradation through over-exploitation. That is why it is important that user communities are involved in water managementdecisions.Natural ecosystems provide many goods and services (functions) to humankind that are oftenneglected in (economic) planning and decision making.

Regulation functions Habitat functions Production functions aesthetic functions

AGRICULTURE Impact of agriculture on the environment is of major importance

The agriculture sector is most important as a user of water and has heavy impacts. Abstraction ofwater for agriculture is leading to dried up rivers, falling ground water tables, salinated soil andpolluted waterways. Carefully considered multipurpose projects can combine irrigation withaquifer recharge, land drainage and ecosystem sustenanceURBAN WATER USESUrban water uses, in particular wastewater effluents, pollute downstream ecosystems if notsufficiently treated. The treatment of effluents is often costly and, especially in developingcountries, not considered a high priority given other needs. Effluent recycling and reuse are oftenseen to be cost-effective conservation measures.

HYDROPOWERHydropower sector affects water regime by changing the water and sediment regime and blockingmigratory movements of fish and amphibians. In some cases reservoirs have provided newhabitats for animals and investments have been made in environmental protection upstream.Combining considerations of power generation, flood control and ecosystem protection can meannew operational rules for reservoir releases.

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INDUSTRYIndustry affects water quantity and quality. Industry often has substantial impacts on waterresources downstream through water use and pollution. Mining, for example, has affected manywaterways in Latin America. In Western Europe industrial pollution has taken its toll on aquaticecosystems during the last century. In many developing countries management of industrialwaste is not yet in place.

Barriers for implementation of IWRM Lack of awareness

Lack of awareness among all water users is the biggest obstacle to change

Lack of political willLack of political will to combat vested interests is also an important barrier. Often theinterests that prevail are not necessarily the most critical ones.

Lack of human and financial resourcesLack of human and financial resources causes integrated water resources management notto be taken into account in planning and development

Implication for change

Recognition of sector needsMajor requirement of IWRM water sector reform is to provide recognition of varying needs andincorporate them in planning e.g. domestic, industrial and agricultural water users.

Legislative adaptationsNational legislation often needs to be harmonised and strengthened to provide vehicle forimplementation of IWRM. Too many conflicting arrangements hinder adoption of IWRM

Institutional adaptationsWater institutions need to function more and more as brokers between various other governmentand stakeholders, rather than stand-alone units. Change in institutional framework must allowcooperative management and negotiation of water rights

Capacity buildingThe above requires a substantive capacity building in facilitation, mediation, negotiation andsurveillance. At present, both users and professionals are often not well equipped to take onthese responsibilities as they require knowledge and skills beyond those traditionally taught to anengineer or hydrologist

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Water sector reforms in Kenya

Kenya is classified a water scarce country with an annual per capita of about 685 m3. Against thisbackground, several problem persist, these include Catchments degradation; Drying up of Rivers, Receding of lake levels, Heavy siltation in dams and pans meant for both hydropower generation and water supplies, Deterioration of our water qualities, Increased water use conflicts due to competition of the little available water resources, Damaged roads, railway lines, bridges, buildings, farmland, water intakes and people displaced

due flash floods,

In addition the levels of water services provision were faced with problems including; Lack of adequate and continued dwindling financial resources in the water sector, Dilapidated infrastructure and low revenue collection to augment and maintain the existing

water supplies and to extend the water coverage, Increasing number of people unserved in urban and rural areas and, Absence of autonomous institutions to manage water supply and sewerage services in our

cities and most urban areas.

The Water Act 2002 was developed with mind of facilitating the management of the countrys waterresources in a sustainable manner and ensue access to adequate water supply and sewerage by thepopulation.

Until the water reforms were implemented the laws in existence were inadequate becauseo there were too many legal provisions dealing with Water, often conflicting, hence difficulties in

enforcemento Many different actors, whose activities conflict, and no mechanism for resolutionso Ministry of Water handled policy, regulation and service provision, hence no distinction

between water resources management, development and service provisiono A supply-driven environment, with serious consequences on sustainability and efficiency of

usage of the resourceo The overlapping roles and responsibilities of key public actors in the water sector were the

main causes of conflicts and poor services in the sector

The management strategy under the water Act 2002 allowed for creation of the Water Services Boardto oversee the supply of water and sewerage services while the management of the water resourceswas vested on an autonomous Water Resources Management Authority.

The Water Act 2002 therefore provides for separation of roles and clarifies entitlement policy formulation that remains with government ministry responsible for water regulation and management of water resources and service provision devolved to autonomous

bodies participation of users through the water users association and catchments advisory

committees Decentralization of water resources management and service provision to drainage areas.

The Water Resources Management Authority manage, protect and conserve our water resources

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The authority have regional offices at the catchments level for decentralized decision makingfor quick response to water resources management problems and to speed the waterallocation process along the river basin equitably.

The Water Services Board Regulator for water services as licensees, responsible for the efficient and economical

provision of water services by engaging an agent or water service provider to give waterservices within its area of jurisdiction.

Agents include Local Authorities or public water companies formed for that purpose, privatecompanies, community organizations or NGOs

Catchment Area Advisory Committees (CAACs) and Water users Association

Ensure community participation in both the management of the resources and development.

CAACs advise the WRMA at the appropriate regional office concerning: Water resources conservation, use, and apportionment The grant, adjustment, cancellation or variation of any permit

Water Users Associations serve as forum for conflict resolution as well as co-operativemanagement of the resource in catchment areas

Water Appeals Board An independent body to resolve disputes between holders of water rights and the others.

Water Services Trust Fund To assist in financing the provision of water services to areas of Kenya which are without

adequate water services in particular the poor communities

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Graphical representation of the management structure under old water laws

Core problems: Inadequate and insufficiently harmonized legal and institutional frameworks Overlapping responsibilities Inefficient operational and financial management systems Institutional /management conflicts

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INSTITUTIONAL SET-UP UNDER WATER ACT 2002

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THE WATER BALANCEThe water balance is an accounting of the inputs and outputs of water. The water balance of a place,whether it be an agricultural field, watershed, or continent, can be determined by calculating the input,output, and storage changes of water at the Earth's surface. The major input of water is fromprecipitation and output is evapotranspiration. The geographer C. W. Thornthwaite (1899-1963)pioneered the water balance approach to water resource analysis. He and his team used the water-balance methodology to assess water needs for irrigation and other water-related issues.

To understand water-balance concept, we need to start with its various components:Precipitation (P). Precipitation in the form of rain, snow, sleet, hail, etc. makes up the primarilysupply of water to the surface. In some very dry locations, water can be supplied by dew and fog.Actual evapotranspiration (AE). Evaporation is the phase change from a liquid to a gas releasingwater from a wet surface into the air above. Similarly, transpiration is represents a phase change whenwater is released into the air by plants. Evapotranspiration is the combined transfer of water into theair by evaporation and transpiration. Actual evapotranspiration is the amount of water delivered to theair from these two processes. Actual evapotranspiration is an output of water that is dependent onmoisture availability, temperature and humidity. Think of actual evapotranspiration as "water use", thatis, water that is actually evaporating and transpiring given the environmental conditions of a place.Actual evapotranspiration increases as temperature increases, so long as there is water to evaporate andfor plants to transpire. The amount of evapotranspiration also depends on how much water is available,which depends on the field capacity of soils. In other words, if there is no water, no evaporation ortranspiration can occur.Potential evapotranspiration (PE). Potential evapotranspiration is the amount of water that would beevaporated under an optimal set of conditions, among which is an unlimited supply of water. Think ofpotential evapotranspiration of "water need". In other words, it would be the water needed forevaporation and transpiration given the local environmental conditions. One of the most importantfactors that determines water demand is solar radiation. As energy input increases the demand forwater, especially from plants increases. Regardless if there is, or isn't, any water in the soil, a plant stilldemands water. If it doesn't have access to water, the plant will likely wither and die.Soil Moisture Storage (ST). Soil moisture storage refers to the amount of water held in the soil at anyparticular time. The amount of water in the soil depends on soil properties like soil texture and organicmatter content. The maximum amount of water the soil can hold is called the field capacity. Fine grainsoils have larger field capacities than coarse grain (sandy) soils. Thus, more water is available foractual evapotranspiration from fine soils than coarse soils. The upper limit of soil moisture storage isthe field capacity, the lower limit is 0 when the soil has dried out.Change in Soil Moisture Storage (DST). The change in soil moisture storage is the amount of waterthat is being added to or removed from what is stored. The change in soil moisture storage fallsbetween 0 and the field capacity.Deficit (D) A soil moisture deficit occurs when the demand for water exceeds that which is actuallyavailable . In other words, deficits occur when potential evapotranspiration exceeds actualevapotranspiration (PE>AE). Recalling that PE is water demand and AE is actual water use (whichdepends on how much water is really available), if we demand more than we have available we willexperience a deficit. But, deficits only occur when the soil is completely dried out. That is, soilmoisture storage (ST) must be 0. By knowing the amount of deficit, one can determine how muchwater is needed from irrigation sources.Surplus (S) Surplus water occurs when precipitation, P exceeds PE and the soil is at its field capacity(saturated). That is, we have more water than we actually need to use given the environmentalconditions at a place. The surplus water cannot be added to the soil because the soil is at its field

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capacity so it runs off the surface. Surplus runoff often ends up in nearby streams causing streamdischarge to increase. Knowledge of surplus runoff can help forecast potential flooding of nearbystreams.

The Earth's Water BudgetWater covers 70% of the earth's surface, but it is difficult to comprehend the total amount of waterwhen we only see a small portion of it. The following diagram displays the volumes of water containedon land, in oceans, and in the atmosphere. Arrows indicate the annual exchange of water between thesestorages.

Diagram adapted from: Peixoto and Kettani (1973)

The oceans contain 97.5% of the earth's water, land 2.4%, and the atmosphere holds less than .001%,which may seem surprising because water plays such an important role in weather. The annualprecipitation for the earth is more than 30 times the atmosphere's total capacity to hold water. This factindicates the rapid recycling of water that must occur between the earth's surface and the atmosphere.

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Computing a Soil - Moisture BudgetThe best way to understand how the water balance works is to actually calculate a soil water budgetusing the example below. To work through the budget, we'll take each month (column) one at a time.It's important to work column by column as we're assessing the moisture status in a given month andone month's value may be determined by what happened in the previous month.

J F M A M J J A S O N D Year

P 50 49 66 78 100 106 88 84 86 73 56 45 881

PE 0 0 5 40 84 123 145 126 85 44 8 0 531

P-PE 50 49 61 38 26 -17 -57 -42 1 29 48 45

DST 0 0 0 0 0 17 57 16 1 29 48 12

ST 90 90 90 90 90 73 16 0 1 30 78 90

AE 0 0 5 40 84 123 145 100 85 44 8 0 634

D 0 0 0 0 0 0 0 26 0 0 0 0 26

S 50 49 61 38 26 0 0 0 0 0 0 33 258

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Soil Moisture Recharge

Water BudgetField Capacity = 90 mm

J F M A M J J A S O N D Year

P 50 49 66 78 100 106 88 84 86 73 56 45 881

PE 0 0 5 40 84 123 145 126 85 44 8 0 531

P-PE 50 49 61 38 26 -17 -57 -42 1 29 48 45

DST 0 0 0 0 0 -17 -57 -16 1 29 48 12

ST 90 90 90 90 90 73 16 0 1 30 78 90

AE 0 0 5 40 84 123 145 100 85 44 8 0 634

D 0 0 0 0 0 0 0 26 0 0 0 0 26

S 50 49 61 38 26 0 0 0 0 0 0 33 258

Start the budget process at the end of the dry season when precipitation begins to replenish the soilmoisture, called soil moisture recharge, in September. At the beginning of the month the soil isconsidered dry as the storage in August is equal to zero. During September, 86 mm of water falls onthe surface as precipitation. Potential evapotranspiration requires 85 mm. Precipitation thereforesatisfies the need for water with one millimeter of water left over (P-PE=1). The excess one millimeterof water is put into storage (DST=1) bringing the amount in storage to one millimeter (August ST =0so 0 plus the one millimeter in September equals one millimeter). Actual evapotranspiration is equal topotential evapotranspiration as September is a wet month (P>PE). There is no deficit during this monthas the soil now has some water in it and no surplus as it has not reached its water holding capacity.During the month of October, precipitation far exceeds potential evapotranspiration (P-PE=29). All ofthe excess water is added to the existing soil moisture (ST (September) + 29 mm = 30 mm). Being awet month, AE is again equal to PE.Calculating the budget for November is very similar to that of September and October. The differencebetween P and PE is all allocated to storage (ST now equal to 78 mm) and AE is equal to PE.Soil Moisture Surplus

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During December, the study area is in winter and the potential evapotranspiration has dropped to zeroas plants have gone into a dormant period thus reducing their need for water and cold temperaturesinhibit evaporation. Notice that P-PE is equal to 45 but not all is placed into storage. Why? At the endof November the soil is within 12 mm of being at its field capacity. Therefore, only 12 millimeters ofthe 45 available is put in the soil and the remainder runs off as surplus (S=33).

Water BudgetField Capacity = 90 mm

J F M A M J J A S O N D Year

P 50 49 66 78 100 106 88 84 86 73 56 45 881

PE 0 0 5 40 84 123 145 126 85 44 8 0 531

P-PE 50 49 61 38 26 -17 -57 -42 1 29 48 45

DST 0 0 0 0 0 -17 -57 -16 1 29 48 12

ST 90 90 90 90 90 73 16 0 1 30 78 90

AE 0 0 5 40 84 123 145 100 85 44 8 0 634

D 0 0 0 0 0 0 0 26 0 0 0 0 26

S 50 49 61 38 26 0 0 0 0 0 0 33 258

Given that the soil has reached its field capacity in December, any excess water that falls on the surfacewill likely generate surplus runoff. According to the water budget table this is indeed true. Note that inJanuary, P-PE is 50 mm and DST is 0 mm. What this indicates is that we cannot change the amount instorage as the soil is at its capacity to hold water. As a result the amount in storage (ST) remains at 90mm. Being a wet month (P>PE) actual evapotranspiration is equal to potential evapotranspiration.Note that all excess water (P-PE) shows up as surplus (S=50 mm).Similar conditions occur for the months of February, March, April, and May. These are all wet monthsand the soil remains at its field capacity so all excess water becomes surplus. Note too that the valuesof PE are increasing through these months. This indicates that plants are springing to life andtranspiring water. Evaporation is also increasing as insolation and air temperatures are increasing.Notice how the difference between precipitation and potential evapotranspiration decreases throughthese months. As the demand on water increases, precipitation is having a harder time satisfying it. Asa result, there is a smaller amount of surplus water for the month.Surplus runoff can increase stream discharge to the point where flooding occurs. The flood durationperiod lasts from December to May (6 months), with the most intense flooding is likely to occur inMarch when surplus is the highest (61 mm).

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Soil Moisture Utilization

Water BudgetField Capacity = 90 mm

J F M A M J J A S O N D Year

P 50 49 66 78 100 106 88 84 86 73 56 45 881

PE 0 0 5 40 84 123 145 126 85 44 8 0 531

P-PE 50 49 61 38 26 -17 -57 -42 1 29 48 45

DST 0 0 0 0 0 -17 -57 -16 1 29 48 12

ST 90 90 90 90 90 73 16 0 1 30 78 90

AE 0 0 5 40 84 123 145 100 85 44 8 0 634

D 0 0 0 0 0 0 0 26 0 0 0 0 26

S 50 49 61 38 26 0 0 0 0 0 0 33 258

By the time June rolls around, temperatures have increased to the point where evaporation isproceeding quite rapidly and plants are requiring more water to keep them healthy. As potentialevapotranspiration is approaching its maximum value during these warmer months, precipitation isfalling off. During June P-PE is -17 mm. What this means is precipitation no longer is able to meet thedemands of potential evapotranspiration. In order to meet their needs, plants must extract water that isstored in the soil from the previous months. This is shown in the table by a value of 17 in the cell forDST (change in soil storage). Once the 17 m is taken out of storage (ST) it reduces its value to 73.The month of June is considered a dry month (P

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Soil Moisture Deficit

Water BudgetField Capacity = 90 mm

J F M A M J J A S O N D Year

P 50 49 66 78 100 106 88 84 86 73 56 45 881

PE 0 0 5 40 84 123 145 126 85 44 8 0 531

P-PE 50 49 61 38 26 -17 -57 -42 1 29 48 45

DST 0 0 0 0 0 -17 -57 -16 1 29 48 12

ST 90 90 90 90 90 73 16 0 1 30 78 90

AE 0 0 5 40 84 123 145 100 85 44 8 0 634

D 0 0 0 0 0 0 0 26 0 0 0 0 26

S 50 49 62 38 26 0 0 0 0 0 0 33 258

August, like June and July, is a dry month. Potential evapotranspiration still exceeds precipitation andthe difference is a -42 mm. Up until this month there has been enough water from precipitation andwhat is in storage to meet the demands of potential evapotranspiration. However, August begins withonly 16 mm of water in storage (ST of July). Thus we'll only be able to extract 16 mm of the 42 mm ofwater needed to meet the demands of potential evapotranspiration So, of the 42 mm of water we wouldneed (P-PE) to extract from the soil. In so doing, the amount in storage (ST) falls to zero and the soil isdried out. What happens to the remaining 26 mm of the original P-PE of 42? The unmet need for watershows up as soil moisture deficit. In other words, we have not been able to meet our need for waterfrom both precipitation and what we can extract from storage. AE is therefore equal to 100 mm (84mm of precipitation plus 16 mm of DST).

Conjunctive use of groundwater and surface waterThe principles of hydrological cycle call for integration between surface and groundwatermanagement. An aquifer undisturbed by pumping is in approximate equilibrium and water is added bynatural recharge and removed by natural discharge. In response to periods of abundant precipitation,the water table levels rise and in time of drought, the water level declines. When well is introduced in alocation within the catchment, new conditions are created. Some water will be removed from thestorage in the aquifer in response to reduced head in the vicinity of the well and may induce increasedrecharge from precipitation or from streams or it may decrease natural discharge into streams orsprings. If discharge far exceeds the recharge, the withdrawals will cause adjustments in the wateraquifer to a point where significant volumes of water are removed from storage over large portions of

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the aquifer. The consequences of such withdrawals include; increased cost of pumping, for existingwells, harmful depletion of stream flow, land subsidence, and intrusion of low quality waters.The concept of safe yield is therefore used to express the quantity of ground water that can bewithdrawn without impairing the aquifer as a water source, causing contamination, or creatingeconomic problems from increased pumping lift. Safe yield will depend on the availability of water forrecharge, transmissivity of the aquifer and in some cases; the safe yield is limited by potentialcontamination.

If the rate of recharge of an aquifer is increased, the safe yield is also increased, if an aquifer oflow transmissivity can be recharged close to the point of withdrawal, the safe yield may also beincreased. In addition, enhanced recharge may allow an aquifer to function as storage reservoir.In addition to augmentation discharge to surface stream flow especially during low flow seasons,there are several advantages in storing water underground. The cost of recharge may be lessthan the cost of construction of surface reservoirs, the acqifer also serve as distribution systemand eliminates the need of pipelines besides, water in surface reservoirs is subject to evaporationand contamination, which is not the case with groundwater storage. Hence optimal waterresources management in a catchment nearly always involve conjunctive use of surface andground water.

Artificial recharge may be used to enhance infiltration to groundwater storage; either by means ofrecharge well or infiltration field. In this case, surface water is diverted to permeable groundwhere it infiltrates to the groundwater. In areas where percolation rates are low or whererecharge route is via beds of river channels, surface reservoirs may be used to store water duringhigh flow when flow exceeds the percolation capacity of the channel. This water is then releasedfor percolation when the natural stream is low.

It clears therefore that conjunctive use of surface and groundwater resources help to achievesustainable use of both ground and surface water sources

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Watershed based planning

Hydrology is the science of water that is concerned with the origin, circulation, distributionand properties of waters of the earth and regional hydrology is the branch of hydrology whichdeals with the effects of land management and vegetation on the quantity, quality and timingof water yields - including floods, erosion and sedimentation

Watershed, or catchment, is a topographic area that is drained by a stream, that is, the totalland area above some point on a stream or river that drains past that point. The watershed orcatchment is often used as a planning or management unit.

River basin is a larger land area unit that, although comprised of numerous sub watershedsand tributaries still drains the entire basin past a single point. Land use, management andplanning is often diverse and complex.

Watershed management is the process of guiding and organizing land and other resourceuse on a watershed to provide desired goods and services without affecting adversely soiland water resources

Watershed management practices are those changes in land use, vegetative cover, andother nonstructural and structural actions that are taken on a watershed to achieve watershedmanagement objectives. Integrated catchment management therefore is defined as thecoordinated and sustainable use and management of land, water, vegetation and othernatural resources on a water catchment basis so as to balance resource utilisation andconservation.

Water as a resourceWater is the most important and most absolutely necessary natural resource required byman. When human demands for water are not met, there are problems . Extent of worldwidewater supplies; over 97 percent of the water on earth (air and land) is salty and therefore notavailable to meet our demands Only 2.6 percent is fresh water of this, 77 percent is tied up inglaciers and polar ice caps, 11 percent more is stored in deep ground water and is generallynot available only 12 percent is left for circulation. Most of this however, is locked up frommanagement or manipulation in lakes, reservoirs, soil and groundwater storage. Only 0.57percent enters into the hydrologic cycle within the atmosphere and biosphere

The atmosphere is involved through the ET and precipitation processes. The biosphereextends from the bottom of the rooting zone to the top of the plant canopy. This is the portionof the water on the earth's surface that can be affected by watershed management,particularly the manipulation of the vegetation

How is this "usable" water distributed on a national basis or catchment basis? Water Balance a process model based on monthly values of temperature, precipitation and local soilmoisture storage capacity is useful to answer this question.The hydrologic cycle can be expressed as a continuity equation for any large or smalllocation. It follows the conservation of mass law which simply stated means that the water inthe hydrologic cycle is always accountable

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The most common form of the so-called water balance equation is:P - ET = Q

or, the amount of precipitation on any land mass minus the amount of that water loss toevapotranspiration must provide the watershed output, runoff Precipitation represents theequation (and watershed) inflow and ET and Q represent the outflows

For any finite period of time, less than needed to establish the long term average quantitativebalance above, the equation for any area becomes:

P -(ET + Q) = + S

where the inflow and outflows don't balance and whatever the difference, either plus or minusgoes into or comes out of storage to make the continuity law work. This site of storagechange for a watershed or river basin is the soil and bedrock aquifers. In any location thequantities within the equation particularly the ratio of P input to ET output to the atmospheredetermines how much, on an average, is available for Q to meet our supply demands. Ofequal importance is the distribution over time of both P and ET

does the precipitation come when the ET demands are high or low? rainfall does not fall uniformly over time for any location likewise, ET rates vary with time of day and season of the year the time of the precipitation with respect to time of year and temperature effects the

form of precipitation (snow?) which may in itself determine whether it is immediatelyavailable for runoff

neither P nor ET are distributed uniformly spatially over the watershed

Watershed based planning promotes decentralisation of planning and management for thefollowing advantages;

Diversity between localities- demand for public services vary from place to place bothin quantity and quality, decentralisation can ensure efficient response to this variationin demand

Efficiency- Locally financed and provided services can be produced at a lower costand enhance community participation as well as voluntary organisation in such a wayas to reduce the costs significantly

Accountability- Decentralised institutions are more accountable to its constituents dueto proximity of the service providers to the served people. The people also have abetter understanding of how the institutions operate

Co-ordination- Since many local services are interdependent, co-ordination of servicescan results to cost saving. Co-ordination is much easier to attain in a decentralisedsystem