WNHN Model Report

1
WNHN Model Report

• Key Features
• 150 miles by 150 miles
• One-half mile uniform grid cells
• Five Layers D, N, three for Carmel/Wanakah
• Steady State (gt1956) simulation
• Historical Transient (1956-2000) simulation

2
WNHN Model Report

• Natural Flow Components
• Recharge
• diffuse precipitation
• San Juan River on far NE edge
• Discharge and evaporation
• numerous seeps
• springs
• canyons
• Discharge to Colorado and San Juan Rivers

3
WNHN Model Report

• Human-Imposed Flow Components
• Inflow/Outflow along Lake Powell south shore
• Pumping
• Peabody Western Coal Company
• Indian Municipal
• Windmills

4
WNHN Model Report

• Model Parameters Hydraulic Conductivity
• D-Aquifer System
• 0.03 to 0.2 ft/day for horizontal hydraulic
  conductivity
• 1/10 of horizontal for vertical hydraulic
  conductivity
• Carmel/Wanakah Aquitard
• 1- 5 x 10-3 ft/day for horizontal hydraulic
  conductivity
• 1- 5 x 10-7 ft/day for vertical hydraulic
  conductivity
• N-Aquifer System
• 0.05 to 1 ft/day for horizontal hydraulic
  conductivity
• 1/10 of horizontal for vertical hydraulic
  conductivity

5
WNHN Model Report

• Model Parameters Storage
• Specific Storage 10-7 ft-1
• Specific Yield 0.1

6
WNHN Model Report

• Recharge
• 0.5 percent of precipitation in lower-elevation,
  lower precipitation areas
• 3-4 percent of precipitation on highest plateaus
• Bands of higher recharge around extensive
  laccoliths
• gt90 loss to surficial and shallow ET addressed

7
WNHN Model Report

• Evapotranspiration
• Extension of usual model simulation of ET
• Seeps, springs and small canyon flows evaporate
  in short order
• Direct evaporation and transpiration from water
  table is also simulated

8
WNHN Model Report

• Calibration to steady state (lt1955)
• 377 data points
• Standard Deviation of Residuals (RSD) 119 feet
• Calibration to historical transient period
  (1956-2000)
• 2373 points from 37 wells
• RSD 57 feet
• Tabulations of Spring simulations yet to come

9
WNHN Model Report

• Current Status
• Report has been through preliminary review by HDR
  and USBR
• Report out for review and comment by TSG
• Next Steps
• Compile and evaluate TSG review comments
• Run model with baseline (2000 continued) and most
  likely demand conditions
• Evaluate key components determining response to
  pumping
• Drawdown
• Impacts on POS Springs
• Decide on model enhancements

10
N-Aquifer Impact Criteria

• Drawdown
• Sustained flow rates
• Compaction
• Increased pumping lifts
• Spring Flows
• Ecosystems
• Water Quality
• Current
• Movement
• Economic