Treasure Valley Hydrologic Project Tasks

The following tasks, identified and described in greater detail within the links, are designed to meet the four specific objectives set forth in the Purpose and Objectives. Many of the tasks are interrelated and will be conducted in parallel. The list of tasks includes:

Hydrogeologic Characterization

Ground water in the Treasure Valley flows in an extremely complex hydrogeological environment. Different characterization approaches yield different types of information.

• Subsurface characterization includes geologic mapping, construction of cross sections, and geophysical investigations.
• Ground water flow directions and changes in water level trends and storage are determined on the basis of ground water level monitoring.
• Water chemistry analyses provide information about flow characteristics, ground water residence times, and water quality.

Stratigraphic Cross Sections

Geologic characterization has included the construction of a series of north-south cross-sections spanning the Treasure Valley, a series of geologic contact maps, and interpretation of the lacustrine/deltaic environment in which Treasure Valley sediments were deposited.

Geophysics

The Center for Geophysical Investigations of the Shallow Subsurface (CGISS) of Boise State University has conducted several seismic surveys in the Treasure Valley. The surveys help delineate subsurface stratigraphy in a highly complex geologic environment.

Ground Water Level Monitoring

Water levels in approximately 70 wells are being measured on a monthly basis. Hydrographs based on the monthly measurements are compiled semi-annually, showing water level changes over time.

Seven mass ground water level measurements have been conducted using approximately 300 wells. The wells were measured within one-week time periods during the Spring and Fall of 1996, 1998, 2000, and during Fall 2001. The mass measurements provide the basis for defining regional water level surfaces.

Potentiometric surface maps of the mass-measurement water level data have been developed for three general depths (shallow, intermediate, and deep). The potentiometric surface maps indicate the direction of ground water flow within different aquifer zones.

Four multi-level ground water monitoring wells have been established as part of this project.

Water Chemistry Analyses

Isotope chemistry was used to estimate ages of Treasure Valley ground water. The survey was used to (1) examine the influence of water originating in the vicinity of the New York Canal (NYC) on the underlying regional ground water flow system using 3H analysis and (2) analyzing the distribution of 14C ground water ages in the central-basin.

Water Budget Development

A water budget initially of estimates of Treasure Valley aquifer system inflows and outflows was developed using 1996 data, but has been updated to 2000 data. The water budget includes estimates of canal seepage, recharge from rivers and streams, recharge from Lake Lowell, subsurface inflows (i.e., underflow), recharge from precipitation and surface water irrigation, and recharge from rural domestic septic systems. The water budget also contains estimates of municipal, self-supplied industrial, irrigation, and rural domestic ground water withdrawals, and ground water discharge to Treasure Valley rivers and drains.

• Water Budget for the Treasure Valley Aquifer System, 1996 & 2000

Numerical Modeling

A numerical model was constructed to simulate ground water flow in the Treasure Valley. Primary objectives of the modeling process were to:

1. Evaluate potential changes in ground water levels from increased withdrawals.
2. Evaluate potential changes in recharge from urbanization.
3. Create an external database allowing rapid model reconstruction for addressing specific local questions.

The model was calibrated using an automated parameter estimation code (PEST) to better define model uncertainty and predictive confidence.

Ground Water Level Monitoring

Water levels in approximately 70 wells are being measured on a monthly basis. Hydrographs based on the monthly measurements are compiled semi-annually, showing water level changes over time.

Seven mass ground water level measurements have been conducted using approximately 300 wells. The wells were measured within one-week time periods during the Spring and Fall of 1996, 1998, 2000, and during Fall 2001. The mass measurements provide the basis for defining regional water level surfaces.

Potentiometric surface maps of the mass-measurement water level data have been developed for three general depths (shallow, intermediate, and deep). The potentiometric surface maps indicate the direction of ground water flow within different aquifer zones.

Four multi-level ground water monitoring wells have been established as part of this project.

Multi-Level Monitor Wells

Four multi-completion monitoring wells (TVHP #1, TVHP #2, TVHP #3, and TVHP #4) were constructed as a part of the project. The purpose of the wells was to provide water level and chemistry data at different depths and locations within the aquifer system.

• Characterization of Ground Water Flow in the Lower Boise River Basin (Petrich and Urban, 2004) - A detailed description of the wells.
• Appendix C. Construction Details for Dedicated, Multi-Level Piezometers - Construction details including geophysical and stratigraphic data for each of the wells.

Information Management and Data Support

This task consists of assembling information and data collected during the course of this project into a comprehensive, accessible database. The task, described in further detail below, consists of:

1. Assembling all spatial data created and/or used in the TVHP into an organized, annotated directory, with complete metadata.
2. Creating a database of selected well information in the Treasure Valley.
3. Creating GIS tools for assembling model files from GIS spatial data.
4. Creating a web site describing general ground water conditions in the Treasure Valley, and describing the TVHP.
5. Expanding the web site to include GIS and other project data.

Public Outreach

Public outreach has consisted of numerous presentation, newspaper articles, journal publications, and displays. A key outreach event was the Treasure Valley Water Summit - a community discussion about water and water issues in the Treasure Valley.

• Summary of the Treasure Valley Water Summit - January 14-15, 2002