1. A Review of Recent Water Level Changes In the Denver Basin Bedrock Aquifers Daniel O. Niemela and Christopher J. Sanchez Bishop-Brogden Associates, Inc

2. Overview Bishop-Brogden Associates, Inc Denver Basin Aquifer Hydrogeology Example Hydrograph Maps of Decline Rates in Each Aquifer Water Use Management

3. Denver Basin Aquifers Source: USGS HA-730-C Bishop-Brogden Associates, Inc Confined Aquifer System Heterogeneous Major Water Source for Front Range Development Non-Renewable Resource 50k - 100k af/yr Pumping (SEO and Others) Developed with Municipal Style Wells (50 – 800 gpm) Substantial Drilling Cost

4. Denver Basin Aquifers Source: USGS HA-730-C Bishop-Brogden Associates, Inc Interbedded Sandstone, Shale and Clay Aquifers Dawson Aquifer Limited Extent Denver Aquifer Discontinuous Sands Arapahoe Aquifer Most Productive Laramie-Fox Hills Aquifer Widespread

5. Water Level Data Data Sources Colorado Division of Water Resources Data (Annual Report) Municipalities (Unpublished) Criteria Consistent Water Level Data Well Completed in a Single Aquifer Bishop-Brogden Associates, Inc

6. Water Level Decline Well-to-Well Impacts System not at “Steady State” Decreased Available Drawdown Decreased Well Yield Increased Pumping Costs Increased Maintenance

7. Dawson Aquifer Decline Rates Between zero and 10 feet per year Greatest Decline near Fringe and Front Range Urban Corridor Some Ground Water Level Rises Recorded Bishop-Brogden Associates, Inc

8. Denver Aquifer Decline Rates Between zero and 40 feet per year Greatest Decline Rates near Centers of Pumping Inconsistent Data Discontinuous Sand Lenses Bishop-Brogden Associates, Inc

9. Arapahoe Aquifer Decline Rates Between zero and 50 feet per year Greatest Decline Rates are in South Metro Denver Most Productive Aquifer High Decline Rates are Not Basin Wide Some Ground Water Level Rises Recorded Denver Metro Less than 5 ft/yr rise Water Level Above Top of Aquifer at Most Locations Bishop-Brogden Associates, Inc

10. Laramie-Fox Hills Aquifer Decline Rates Between zero and 40 feet per year More Widespread Declines Water Level Above Top of Aquifer at Most Locations Bishop-Brogden Associates, Inc

11. Trends High Decline Rates are Localized Result of Sole Reliance on Denver Basin Water Well-to-Well Interference Complex Nature of the Aquifers Anomalies in Denver Aquifer Result of Discontinuous Aquifer Sands? Bishop-Brogden Associates, Inc

12. Management Good Water Level Record Keeping Project Future Water Levels Evaluate Timing for Renewable Supplies Efficient Water Use Reuse Develop Renewable Supplies Conjunctive Use Aquifer Storage Recovery (ASR) Bishop-Brogden Associates, Inc

13. Conclusions Denver Basin Water Level Declines are Occurring Declines are Localized in some Aquifers Greatest Declines near Greatest Pumping Supply System Planning may Extend Usable Life of Resource Municipalities are Actively Pursuing Renewable Supplies Bishop-Brogden Associates, Inc