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('.J ~ <.C ,...::> ';.=' -, ,- WATER QUALITY MONITORING PLAN Purpose: The Stage One area, Grand Valley Unit, will be monitored before, during, and after construction to determine the effectiveness of Water Systems Improvements in reducing the salt load going into the Colorado River. This report covers the existing and proposed monitoring system required for con- t inued Water and Power Resources Service involvement under Pub I ic Law 93-320. Methodology: Two methods will be used to monitor Grand Valley Unit Stage One. Direct measurement of the salt load will be used, where possible and indicators will be used to show that changes in the ground-water volume have begun. The primary direct measurement will be at the mouth of the Reed Wash study area. Continuous flow measurements are recorded by a Geological Survey (GS) gage, and water quality measurements are monitored with an electrical conduc- tivity (EC) recorder. The EC readings are correlated with weekly total dls- solved solids (TDS) samples. A measurable decrease in the salt load is expec- ted to appear at Reed Wash outlet within a year following completion of con- struction. It will take several years before all the effects of the project are realized. Another item of direct quantitative measurement will be the water and salt budget of the Reed Wash Basin. Direct water quality and quantity measurements will be made at the hydrological boundary of Reed Wash Basin. Preproject monitoring during 1976 provided adequate data for a budget which has been used to predict the results of Water System Improvements (WSI) (Definite Plan Report, "Stage One Development - Grand Valley Unit", March, 1980). Post construction budgets should verify and document these estimates. The water and salt budgets require an extensive data-collection network. The preproject conditions are based on data collected for the Definite Plan 1