Mohammad Rayej, Ph.D., P.E.

Senior Engineer, W.R.

California Dept. of Water Resources

Water Evaluation And Planning Model

Developed by Stockholm Environment Institute (SEI) in 1988

Integrated water Supply-Demand model

Supply allocation driven by water demand priorities, supply preferences and system constraints

Conservation of mass and LP optimization solver to maximize demand coverage subject to constraints Highly scale-able in space & time steps ◦ City, Province, Region, Country ◦ Day, week, month, Year

River hydraulics Hydrologic basins & catchments Rainfall-Runoff process Snowpack accumulation & snowmelt (Climate

Change) Irrigation process (Urban landscape & Ag) Groundwater aquifers (Natural & Artificial

Recharge) Dams & Reservoir operations Surface-Groundwater Interaction (Conjunctive Use) Hydropower generation Water quality and pollution (water temp, DO, BOD,

TDS, First-Order decay)

Current and future water supply and demand conditions ; a time-step model.

Very powerful in building future water scenarios under different population growth, socio_economic and climate change scenarios.

Explores water management strategies (demand reduction, supply augmentation, pollution control).

Long term water planning tool for water managers and governments.

WEAP- HR ◦ 10 Hydrologic Regions ◦ Monthly Time Step ◦ Future urban (indoor, outdoor) and Ag demand ◦ Under urban growths and climate change scenarios

WEAP- PA ◦ Central Valley planning area scale ◦ Sacramento River, San Joaquin, Tulare Lake ◦ Monthly Time step ◦ Future water supply and demand conditions ◦ Evaluate management strategies (supply and demand

options) ◦ Assess system reliabilities and vulnerabilities

1- Rainfall-Runoff “Catchment” Method (Green dots !!!)

Approach: Uses so called “2-bucket” approach to perform soil moisture mass

balance in the root zone and deep percolation over time

Physically based; includes soil, plant and climate and irrigation parameters

Computes crop ET, surface runoff, subsurface lateral flow to surface stream, deep percolation to GW.

Very suitable for climate change scenarios

Input Parameters:

Plant (land use area, Kc, leaf area index to control surface runoff)

Soil (soil moisture capacity, soil hydraulic conductivity, initial moisture content)

Climate (precip, temp, RH, wind speed, melting point and freezing point temperature for snowmelt runoff and snowpack accumulation)

Irrigation (low and high threshold of soil moisture to start or stop irrigation)

Output: Demand volume (Acre-ft)

Dynamically linked to USGS 3-D GW Model (MODFLOW) and MODPATH (GW Particle Tracking) ◦ Every time step

◦ Surface-GW Interactions

WEAP gives surface flow – MODFLOW returns GW flow

◦ Multiple pumping sites and interactions

◦ 3-D GW water level surface

◦ Flow path of pollutants and tracers

WEAP project layout, schematics, and results saved (.kmz file), exported to Google Earth

WEAP results for each supply and demand sites can be viewed on Google Earth

The .kmz file can be sent globally via internet to clients and colleagues for viewing on Google Earth without any need for knowledge of WEAP or the software itself.

WEAP was successfully applied as an integrated water resources model for California Water Plan.

Current and future water supply and demand were quantified under multiple urban growth and climate change scenarios

Several management strategies on supply and demand were evaluated to assess system vulnerabilities as part Robust Decision Making (RDM)