Example - Use of a simulation- optimization approach to assess potential strategies for ground- water management in the Albuquerque area, New Mexico.

Example - Use of a simulation-Example - Use of a simulation-optimization approach to assess optimization approach to assess potential strategies for ground-potential strategies for ground-

water management in the water management in the Albuquerque area, New MexicoAlbuquerque area, New Mexico

Laura Bexfield, Wesley Danskin, and Laura Bexfield, Wesley Danskin, and Doug McAdaDoug McAda

In cooperation with the City of AlbuquerqueIn cooperation with the City of Albuquerque

Background on Background on Management Management

IssuesIssues• City of Albuquerque City of Albuquerque

has historically relied has historically relied on ground water onlyon ground water only

• Up to ¾ of known Up to ¾ of known basin-wide pumping is basin-wide pumping is by COAby COA

• Water-level declines Water-level declines have become large have become large and extensiveand extensive

• COA concerned about COA concerned about subsidence, increasing subsidence, increasing pumping costs, pumping costs, declining water qualitydeclining water quality

Water-level declines (ft), 1960 to 2002Water-level declines (ft), 1960 to 2002

Study ObjectivesStudy Objectives• Quantify likely effects of Quantify likely effects of

overall change in COA overall change in COA water-management water-management strategy on the regional strategy on the regional river-aquifer systemriver-aquifer system

• Determine optimal Determine optimal pumping strategies to pumping strategies to achieve specified achieve specified management objectives management objectives for the regional systemfor the regional system

Available Tools—Available Tools—Flow ModelFlow Model

(McAda & Barroll)(McAda & Barroll)• MODFLOW 2000MODFLOW 2000• 156 rows x 80 columns156 rows x 80 columns• 1 km uniform horizontal 1 km uniform horizontal

spacingspacing• Steady-state and transientSteady-state and transient• Simulates 1900 - 2000Simulates 1900 - 2000• Summer and winter Summer and winter

seasons, 1990 - 2000seasons, 1990 - 2000• Specified-flow and head-Specified-flow and head-

dependent flow boundariesdependent flow boundaries

Objective—Determine optimal Objective—Determine optimal pumping strategies to achieve pumping strategies to achieve

regional management regional management objectivesobjectives

Management ObjectivesManagement Objectives

1.1. Minimize net depletion of aquifer storageMinimize net depletion of aquifer storage

2.2. Minimize net infiltration from the Rio GrandeMinimize net infiltration from the Rio Grande

3.3. Minimize net depletion of aquifer storage, with water-Minimize net depletion of aquifer storage, with water-level constraintslevel constraints

4.4. Minimize net depletion of aquifer storage, with Minimize net depletion of aquifer storage, with constraints on water levels and arsenic concentrationsconstraints on water levels and arsenic concentrations

5.5. Minimize net depletion of aquifer storage after Minimize net depletion of aquifer storage after eliminating river “debt”eliminating river “debt”

Approach to Approach to OptimizationOptimization

• Optimize pumping Optimize pumping for 2006-2040for 2006-2040

• Use projections of Use projections of demand and demand and surface-water surface-water availability provided availability provided by COAby COA

• Use currently Use currently available wellsavailable wells

• Optimize pumping Optimize pumping on an annual basis on an annual basis by well fieldby well field

Key Equations for OptimizationKey Equations for Optimization

Composed of decision variables whose values Composed of decision variables whose values define the solution to the problemdefine the solution to the problem

Objective functionObjective function

Restricts values decision variables can takeRestricts values decision variables can takeConstraintConstraint

Optimization Model DesignOptimization Model Design

• Minimize Minimize objective functionobjective function representing combined representing combined change in aquifer storage (for assigned annual pumping change in aquifer storage (for assigned annual pumping in 25 well fields)in 25 well fields)

• Observe Observe constraintsconstraints on: on:

-Total annual GW demand-Total annual GW demand

-Maximum annual capacity in each well field-Maximum annual capacity in each well field

-Minimum withdrawal from each well field-Minimum withdrawal from each well field

-Water-level decline (no more than 2.5 ft/yr)-Water-level decline (no more than 2.5 ft/yr)• Assume system response a linear function of rate of Assume system response a linear function of rate of

withdrawalwithdrawal

Optimization Model ResultsOptimization Model Results

Optimization Model Results (cont.)Optimization Model Results (cont.)• Recovery of water in storage increased by 242,000 acre-ft Recovery of water in storage increased by 242,000 acre-ft

(more than 2 years of supply)(more than 2 years of supply)• Increased storage recovery derived from increased river/drain Increased storage recovery derived from increased river/drain

leakageleakage

Results for Results for 2006-20402006-2040