Groundwater in Colorado: Hydrogeologic Investigations Supporting Groundwater Administration Kevin Rein, P.E. Deputy State Engineer Colorado Division of Water Resources July 27, 2012

Today’s Discussion Water administration and use in Colorado; water rights Regulation of groundwater use USGS hydrogeologic investigations Role in Colorado water allocation Role in Colorado water planning

Colorado Division of Water Resources

Colorado Water Administration Headwaters State Nine Interstate Compacts 57,000 Water Rights Over 15,000,000 acre-feet delivered annually in state 3,000,000 acre-feet ground water withdrawn annually 275,000 Permitted Wells

Groundwater Use Pre-1960’s, minimal regulation 1960’s: Concern about impacts to surface water rights, Integration of groundwater and surface water administration, Inherently complicated!

Nontributary Groundwater

Key Aspects of Denver Basin Use Recent urbanization relies on Denver Basin groundwater Accessible, both physically and legally Hydrogeologic definition and evaluation of changes through time are critical Groundwater models needed for quantification Northern area South Metro area Monument area

Refine hydrogeologic framework and groundwater movement Estimate groundwater recharge Estimate groundwater withdrawals ( ) Develop 3D computer groundwater flow model Use model to forecast future groundwater depletion. Coordinate with State agencies administering Denver Basin and South Platte groundwater systems USGS Denver Basin Groundwater Availability Project

Nontributary Ground Water Arapahoe Laramie-Fox Hills Dawson South North Denver South Platte River Palmer Divide Lignite zone Denver Basin Cross Section

DWR/USGS Continuing Projects Incorporate Denver Basin model into South Platte model Optimization; pumping rates and locations Generate water level monitoring network Groundwater/surface water interaction Legislative expectations Cooperation, communication, and coordination.

Outcomes Allow an assessment of sustainability Increase sustainability: optimization of pumping Aquifer storage and recovery Groundwater flow model: Local planning; use and alternative supplies Understanding depletive impacts to surface water Integrate Denver Basin into understanding entire South Platte Basin hydrology USGS Denver Basin Groundwater Availability Project

Colorado Water Management The Denver Basin Aquifer System Significant Resource of “great economic importance in Colorado” Significant Resource of “great economic importance in Colorado” Early efforts by USGS and CDWR led to hydrogeologic understanding, clear administration, and efficient allocation Early efforts by USGS and CDWR led to hydrogeologic understanding, clear administration, and efficient allocation Continuing work by USGS and CDWR focuses on refined quantification of resources, optimal use, and local management within the larger basin Continuing work by USGS and CDWR focuses on refined quantification of resources, optimal use, and local management within the larger basin