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The Nexus model is named the Edwards Aquifer and River system Simulation
Model (EDSIMR). The model depicts regional dryland and irrigated farming, water
diversion/pumping, river flows, environmental indicators, aquifer elevation status,
thermal energy cooling, hydropower, and hydraulic fracturing. The model when
solved generates output on water prices, water use, and allocation, farming crop
mix, agricultural production, irrigation strategy, aquifer levels, spring flow discharge
into rivers, farm incomes, municipal and agricultural pumping, pumping lifts,
energy generation, and energy use, among other items.
A FEW Nexus model needs to be based on high-quality data. For the EDSIMR
analysis we needed to integrate data from:
1. Regional aquifer simulations that employed the groundwater model (GAM) to
simulate aquifer level, pump lift and spring flow discharge given alternative
amounts of pumping in the region;
2. Crop growth simulations using EPIC under different irrigation strategies and
climate conditions to develop estimates of dryland and irrigated crop yields
along with water use plus erosion and nutrient flows;
3. River flow and groundwater infiltration where we used SWAT to simulate levels
of aquifer recharge, net inflows at river locations, evaporation, reservoir operations, and water quality characteristics, given changes in agricultural production,
climate and the typical regional distribution of rainfall;
4. Econometric based urban water demand equations that show water demand as a
function of water price and climate conditions;
5. Engineering models of electrical power generation cooling with which we estimated the alternative cooling methods and their implications for water use, cost
and power generation; and
6. Calculations of energy use and water loss associated with many water development alternatives (reservoir construction, pipelines from distant locations,
desalination, aquifer storage, and recovery and conservation incentives among
others).
EDSIMR is formulated as a unifying component that includes modeling of rivers, aquifers, agricultural water use, irrigated and dryland cropping, water project
development, energy generation, cooling water use, cooling water retrofits and nonagricultural water use among other things. That model is used to look at a regional
welfare-maximizing allocation of water across urban, industrial, electrical generating and agricultural users coupled with an optimal choice among the water development and power cooling alternatives. As shown in Fig. 5.3, the total project
encompasses data collection, model development, and feedback from stakeholders.
Key Points
• Nexus analyses can be biased if one neglects product demand and input supply
price-quantity relationships. For example, using US corn for biofuel was a significant force behind corn price increases while the supply of the by-product
glycerol from biodiesel refining reduced glycerol prices. Also, demand quantity
projections may fall if prices are increased as expensively discovered by WPPSS
power suppliers.
B. A. McCarl and Y. Yang
The Nexus model is named the Edwards Aquifer and River system Simulation
Model (EDSIMR). The model depicts regional dryland and irrigated farming, water
diversion/pumping, river flows, environmental indicators, aquifer elevation status,
thermal energy cooling, hydropower, and hydraulic fracturing. The model when
solved generates output on water prices, water use, and allocation, farming crop
mix, agricultural production, irrigation strategy, aquifer levels, spring flow discharge
into rivers, farm incomes, municipal and agricultural pumping, pumping lifts,
energy generation, and energy use, among other items.
A FEW Nexus model needs to be based on high-quality data. For the EDSIMR
analysis we needed to integrate data from:
1. Regional aquifer simulations that employed the groundwater model (GAM) to
simulate aquifer level, pump lift and spring flow discharge given alternative
amounts of pumping in the region;
2. Crop growth simulations using EPIC under different irrigation strategies and
climate conditions to develop estimates of dryland and irrigated crop yields
along with water use plus erosion and nutrient flows;
3. River flow and groundwater infiltration where we used SWAT to simulate levels
of aquifer recharge, net inflows at river locations, evaporation, reservoir operations, and water quality characteristics, given changes in agricultural production,
climate and the typical regional distribution of rainfall;
4. Econometric based urban water demand equations that show water demand as a
function of water price and climate conditions;
5. Engineering models of electrical power generation cooling with which we estimated the alternative cooling methods and their implications for water use, cost
and power generation; and
6. Calculations of energy use and water loss associated with many water development alternatives (reservoir construction, pipelines from distant locations,
desalination, aquifer storage, and recovery and conservation incentives among
others).
EDSIMR is formulated as a unifying component that includes modeling of rivers, aquifers, agricultural water use, irrigated and dryland cropping, water project
development, energy generation, cooling water use, cooling water retrofits and nonagricultural water use among other things. That model is used to look at a regional
welfare-maximizing allocation of water across urban, industrial, electrical generating and agricultural users coupled with an optimal choice among the water development and power cooling alternatives. As shown in Fig. 5.3, the total project
encompasses data collection, model development, and feedback from stakeholders.
Key Points
• Nexus analyses can be biased if one neglects product demand and input supply
price-quantity relationships. For example, using US corn for biofuel was a significant force behind corn price increases while the supply of the by-product
glycerol from biodiesel refining reduced glycerol prices. Also, demand quantity
projections may fall if prices are increased as expensively discovered by WPPSS
power suppliers.
B. A. McCarl and Y. Yang