WATER HARVESTING +
RECHARGE:
Roads for Water &
Sponge Cities
BY LUWIEKE BOSMA– [email protected]
Smart Centre Symposium Mzuzu
Outline
▪ 1. Water harvesting and buffering
▪ 2. Roads for Water
▪ 3. Sponge Cities
▪ 4. Smart Centre integration
The principles of Retention, Recharge and Re-use
1. Water Harvesting and buffering
(Rockstrom et
al. 2007)
Rainfall partitioning
(Source: Mahler)
Water Harvesting
▪ Water Harvesting (WH) refers to the collection of
rainfall for multiple uses, either stored in the soil
profile for immediate uptake by the crop or stored
in a reservoir for future (multiple) uses.
Why doing it?
In arid lands:
• Strong seasonality of precipitation
• Quick runoff and seasonal rivers, dominated by flash floods
• High evaporation rates
• Climate change may result in more extremes
• Potentially the amount of rainwater can meet most of environmental and human needs
• Enormous potential to keep water in the system?
Delft Kitui
Compare for instance Delft (Netherlands)
with Kitui (Kenya)
Why doing it?
In humid zones:
• Dry spells in the dry season
• Risks of erosion and flooding increase
• When more agricultural production takes place on (esp. on
slopes)
• Due to increase of population (e.g. more paved surface)
• Climate change extremes
• Waterborne diseases in surface water can be
prevented if there is a more stable groundwater
table
- The holes need to be closed
(Retention)
- Filling of the bucket must be improved
(Recharge)
- The use of water must be improved
(Reuse)
The water buffer is like an old bucket…3
R A
ctio
ns
What is water buffer management?
▪ Ensure better storage of water in the
landscape; as shallow groundwater, as soil
moisture or in local surface reservoirs:
▪ Multiple sources for multiple uses
▪ Often there is enough rainfall, but not enough
storage
3R Recharge – Retention - Reuse
1. Recharge adds water to the buffer and as such it adds water to the circulation: infiltration of rain and runoff water
2. Retain water in the system: In situ retention slows down the lateral flow of groundwater. This helps pond up groundwater and creates large ‘wet’ buffers. Makes water circulation easier.
3. Reuse the water and make it revolve. Not only reduce the usage, but also ensure circulation. Drainage and waste water is a resource.
3R Retention
Kitchen garden
Bio-digestor
3R in practice
▪ Many technologies available and to be chosen
according to local context and needs;
▪ Many small, cheap measures spread at high
density all over the landscape;
Using roads in a beneficial way for water
harvesting and management
2. Road Water Harvesting
Dream and opportunity
To have roads systematically used for water
recharge/retention, storage and water
management all over the world, especially in Sub
Saharan Africa and Asia and create win-wins
18
Why roads?
▪ Annual investment 1-2 Trillion USD
▪ 40% in developing countries
▪ 1 Billion people totally unconnected
▪ Increased water stress – most poor in water stressed
areas (74%)
▪ &
▪ Annual increase of roads: f.i. 70,000 km in SSA
▪ Water is 35% of damage to paved roads, up to 80%
to unpaved roads
19
Why roads?
▪ now often causing local flooding, water logging
and erosion
➢ This can be turned around in large potential for
water harvesting and water management
20
▪ Roads alter surface hydrology
▪ Changed runoff patterns
▪ Roads affect movement of shallow
groundwater
▪ Degradation of watersheds happens
in many parts of the world
Urgent need to turn things around
Floods
Erosion
Esp feeder roads damaged
Sedimentation
Triple Win
REDUCED WATER
DAMAGE
TO ROADS
(-35%, -80%)
And more reliable
Roads
WATER MANAGED
FOR PRODUCTIVE USE
Rising groundwater levels
and better soil moisture
Water retention
Erosion control
Flood management
REDUCED
DAMAGE FROM ROADS
Through Flooding,
Erosion and Sediment
Deposition
Turning things around: Harvesting water from
roads in Ethiopia – example of impact
▪ Capturing rainfall for dry periodas groundwater, soil moisture or surface water
▪ Implemented since 2014
▪ Withstanding 2015 El Nino
▪ Engaged> 2.75 M people in 2015/7 campaigns
▪ Benefitted 2.4 M people
▪ Guidelines
▪ Outscaling now to Bangladesh, Kenya, Uganda, Malawi, Mozambique, Tajikistan, Zambia, Nepal, Bolivia
Three Approaches
1. Making use of the road as it is for water
management - adaptation
2. Modify and optimize design of the road
3. Additional measures & opportunities
Road water management technique Surface
storage
Soil
moisture
storage
Shallow
groundwater
recharge
1 Flood water spreaders along road
surfaces
2 Flood diversions from culverts and road
drainage
3 Infiltration structures fed from road
drainage
4 Cascading irrigation from road drainage
5 Surface storage fed from road drainage
(borrow pits, ponds and cisterns)
6 Road bodies used as dams
7 Road crossings used as sand dams or as
water spreading structures
Principles of road water harvesting
design
▪ ‘give’ the runoff back to the land / farms
▪ Diversions + spreading to nearby farmland
▪ Prevent rapid draining of water from the watershed
▪ Prevent flood peaks
▪ Rather have the runoff water run in to vegetation
bunds and farm fields or pastures – will also reduce
sediment deposition
▪ Examples from different countries
ETHIOPIA: ROAD WATER HARVESTING CAMPAIGN
ETHIOPIA: CATCHMENT APPROACH
Deep trenches
Culverts
Borrow pit
Communities which used to have been affected
by flooding are saved from flooding.
Uganda: managing rice field with roads
MANY COUNTRIES, CONTEXTS AND SOLUTIONS
Mozambique: low embankment
roads to manage wetlands
Uganda: managing rice cultivation with
roads embankments and culvert
Zambia: Converting borrow pits
Kenya: Road drifts as sand dams
BANGLADESH: USING ROADS AS EFFECTIVE EMBANKMENTS
Synchronized levels
Roads as embankments
Flood shelters
Better protection
KENYA: ROAD RUNOFF COLLECTED IN STORAGE STRUCTURES
Converted borrow-pit
for water storage
On farm pond
collecting road runoff
Opportunity: Road water for wildlife
KENYA: USING CUTOFF TRENCHES TO TAP ROAD RUNOFF
Cutoff from side drain
Excess water redirected
Stored in a trench to
increase soil moisture for
agricultural production
KENYA: USING CULVERTS & DRIFTS
Cross-culvert used to harvest water in a trench
Collecting water from a culvert
Soaking pits along the road for groundwater recharge
and increased soil moisture
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Trenches/Soaking pits for groundwater
recharge and increased soil moisture
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Integrated watershed management
1549630 ha
Diversion from culvert outlet
Many additional opportunities to better use
roads for water
1. Controlled sand mining along roads
2. Evacuation in times of floods
3. Road side tree planting
4. Brick making
5. Biological rodent control
6. Intermediate means of transport
>> We can turn roads into development reservoirs
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Road side tree
planting
Brick making – using runoff sediments
Cost Benefit Analysis
Kitui representative of 8 sub-counties (30
farms)
Mbitini (ward in Kitui County) (60
farms)
Costs: 2440 KSH
Benefits: 7273 KSH
The costs of construction compared with the return on investment after 1
growing season
Beyond techniques, it’s about Governance
▪ 1. Integrate within Programs on Roads and Water and Agriculture
▪ 2. Community engagement
▪ 3. Change procedures in roads development• Manuals
• Investment and maintenance budgets
• Cooperation
▪ 4. Capacity building• Technical training – county staff and road engineers
• Short courses
• Tools (run-off models)
• Guided learning
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For example: Kenya: working as partners with
County Governments and Road Authorities
▪ Technical team in Kitui, Makueni & Machakos
▪ Cross-sectoral coordination and integration
▪ For all activities within the County
▪ Departments of Water, Agriculture, Roads &
Coordination
▪ Representatives of ASDSP and KeRRA
▪ Ongoing links with road Authorities to integrate in
their projects and guidelines
Can we make a water buffer in an urban
environment
3. Sponge Cities
Collecting water from
rooftops
Bridge across seasonal
stream to check and store
seasonal floods Using stormwater for
groundwater recharge
Porous paving for
increased infiltration
Sponge City
▪ Innovative designs are piloted on the base of
detailed research.
▪ The implementation of multiple techniques can be
combined, making up an integrated approach for
storm water management
▪ A guideline on how-to plan sponge towns will be
developed together with the Kajiado sponge city
team and with relevant authorities.
It is about
▪ Creating a buffer – protect and store during rains
& release slowly when it is dry
▪ Diversified supply for multiple uses
▪ Support self-supply
▪ Supporting business and government initiatives
▪ Work with citizen platforms and private households
▪ Skill building of local masons and artisans
Spong city in practice
Focused on 6 techniques:
▪ Roof harvesting systems
▪ Gully plugging – check dams
▪ Ponds for water storage and farming
▪ Kitchen gardening + grey water reuse
▪ Tree planting
▪ Road water harvesting
Kajiado: groundwater recharge
Integrating water harvesting into Smart Centre
technologies and approach
4. Smart centre integration
SC meets RfW and Sponge
Benefits water harvesting & buffering for Smart Centres:
▪ Increase the natural buffer
▪ Make the technologies last longer
▪ E.g. with infiltration pits for recharge the water level in a well/borehole will be higher and more reliable over time
▪ Cost reduction for maintenance?
▪ Opportunity to be involved in practical training on 3R methods, RfW and Sponge?
What could work well?
Make water harvesting part of the package?
▪ Interesting business-model?
▪ E.g. for an extra X USD we add 2 tube wells to your borehole
▪ E.g. for an extra X USD we add a training on water retention and
recharge
▪ E.g. for an extra X USD we will advise on implementing diversions
▪ Provide it as an add-on, e.g. different packages with or
without water harvesting indicating possible life-spans and
costs in the longer term? Provide CBA
▪ Also provide interventions for Roads for Water and Sponge
Cities as stand alone?
How do RfW and Sponge contribute?
▪ Share expertise on road water harvesting and
Sponge Cities
▪ Linkages to farmers, organizations and government
sector interested
▪ Up-scaling and creating more business opportunities
▪ Lobbying and support for resource mobilization
Room for discussion
▪ How can Smart Centre technologies and its
approach also support water harvesting initiatives?
▪ How do you see the business-model of the wider
package that includes water harvesting – is there
interest for this?
▪ Could we have a pool of technicians on water
harvesting specifically?
▪ How to market this opportunity?
▪ Suggestions?
Thank you!