Water-level monitoring and a groundwater model in the Big Wood River Valley Presented by Mike McVay November 5, 2012

IDWR Data Logger Network 13 wells have been instrumented; 5 candidates for future deployment. Data loggers are collecting water level readings two times per day. Downloaded every six months.

Water level trends 1980’s - current

Upper Wood River WMD Well Network 36 wells have been identified as monitoring locations. Semi-annual measurements are proposed for the monitoring frequency.

USGS Synoptic Network Over 90 wells were measured in 2006 and re-measured in October 2012.

Ground Water Model of the Big Wood Valley Collaboration with the USGS synoptic water levels show ground water flow is from north to south.

Why a Model of the Big Wood? Fully allocated resource – Designated GWMA in 1991 Water rights distribution problem – Most proposed transfers involve up-basin movement of PODs Conjunctive administration/management on its way – Delivery calls imminent (Big Wood Canal Company) – 2009 petition for CGWA – Measurement district created in 2011

Why a Model of the Big Wood (cont’d) IDWR needs unbiased, public domain groundwater flow model to evaluate transfers and mitigation requirements Timing good because USGS study nearing completion – Synoptic water level measurement and trend analysis in 2006 – Water Budget report in 2009 – Hydrogeologic Framework report in 2012

The Model A three-year timeframe IDWR collaborating with USGS to develop groundwater flow model with oversight from Technical Advisory Committee Water Board financing with USGS match Used for administration of water – Evaluation of Transfers – Determine Curtailment – Evaluate Mitigation – Won’t be used to determine injury

Technical Advisory Committee Provides transparency and is a vehicle for stakeholder input Likely participants: – Previous USGS Cooperators Cities of Bellevue, Hailey, Ketchum, Sun Valley Nature Conservancy Blaine Soil Conservation District Citizens for Smart Growth Sun Valley Water and Sewer – Big Wood Canal Company – Water District 37? – Technical representatives for others

Summary of Work Plan Additional data collection – Water level synoptic in October 2012 – Streamflow gain/loss surveys in August and October 2012 and March 2013 – Additional wells Form Technical Advisory Committee Construct and calibrate groundwater flow model – Update water budget – Model discretization – Initial parameterization – Calibration Convert Steady State model to transient model

Activities to Date Sponsored 4 new USGS gages in 2010 (North Fork, East Fork, Trail Creek, Warm Springs) Expanded monitoring well network from 6 wells to 18 USGS seepage analysis to quantify reach gains/losses Synoptic water level measurement in 2012 Developed modeling work plan w/ budget and schedule

Products Numerical groundwater flow model Final Report describing model and development Reports describing results of scenarios – Drought – Change in land use – Climate change USGS Fact Sheet Response function maps

Questions?