Transcript Document

Example - Use of a simulationoptimization approach to assess
potential strategies for groundwater management in the
Albuquerque area, New Mexico
Laura Bexfield, Wesley Danskin, and
Doug McAda
In cooperation with the City of Albuquerque
Background on
Management
Issues
• City of Albuquerque
has historically relied
on ground water only
• Up to ¾ of known
basin-wide pumping is
by COA
• Water-level declines
have become large
and extensive
• COA concerned about
subsidence, increasing
pumping costs,
declining water quality
Water-level declines (ft), 1960 to 2002
Study Objectives
• Quantify likely effects of
overall change in COA
water-management
strategy on the regional
river-aquifer system
• Determine optimal
pumping strategies to
achieve specified
management objectives
for the regional system
Available Tools—
Flow Model
(McAda & Barroll)
• MODFLOW 2000
• 156 rows x 80 columns
• 1 km uniform horizontal
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•
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•
spacing
Steady-state and transient
Simulates 1900 - 2000
Summer and winter
seasons, 1990 - 2000
Specified-flow and headdependent flow boundaries
Objective—Determine optimal
pumping strategies to achieve
regional management
objectives
Management Objectives
1.
2.
3.
4.
5.
Minimize net depletion of aquifer storage
Minimize net infiltration from the Rio Grande
Minimize net depletion of aquifer storage, with waterlevel constraints
Minimize net depletion of aquifer storage, with
constraints on water levels and arsenic concentrations
Minimize net depletion of aquifer storage after
eliminating river “debt”
Approach to
Optimization
• Optimize pumping
for 2006-2040
• Use projections of
demand and
surface-water
availability provided
by COA
• Use currently
available wells
• Optimize pumping
on an annual basis
by well field
Key Equations for Optimization
Objective function
Composed of decision variables whose values
define the solution to the problem
Constraint
Restricts values decision variables can take
Optimization Model Design
• Minimize objective function representing combined
change in aquifer storage (for assigned annual pumping
in 25 well fields)
• Observe constraints on:
-Total annual GW demand
-Maximum annual capacity in each well field
-Minimum withdrawal from each well field
-Water-level decline (no more than 2.5 ft/yr)
• Assume system response a linear function of rate of
withdrawal
Optimization Model Results
Optimization Model Results (cont.)
•
•
Recovery of water in storage increased by 242,000 acre-ft
(more than 2 years of supply)
Increased storage recovery derived from increased river/drain
leakage
Results for
2006-2040