WSP07957

• File Number: 8276.100
• Description: Grand Valley Unit-Colorado River Basin Salinity Control Project
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 1/21/1983
• Title: Grand Valley Salt Pickup Calculations - Draft Report
• Water Supply Pro - Doc Type: Report/Study

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CHAPTER I

INTRODUCTION

Background

The construction of the Grand Valley unit is scheduled to be completed

in stages. Stage I, which is presently under construction, involves the

concrete lining of a 6.8 mile section of the Government Highline Canal and

the placement in pipe of 29.7 miles of laterals. Advance planning for the

remainder of the Grand Valley Unit beyond Stage I will be completed during

the construction of Stage I.

All alternatives and increments of alternatives evaluated in the

planning process will be compared in terms of cost effectivlmess. For the

Colorado River Water Quality Improvement Program, cost effectiveness is

defined as the total annual equivalent cost of the alternati.ve or increment

of alternative divided by the the mg/L reduction in total di.ssolved solids

(TDS) concentration at Imperial Dam. To compute the mg/L effect, the salt

load reduction and depletion of each alternative is calculated. These values

are then inserted into standardized Colorado River Basin equations to

determine the effect at Imperial Dam.

To determine the salt load reduction, internal water and salt budget

models are being developed. These models include precipitation, natural

surface inflow, ground water inflow, irrigation diversions, canal seepage,

lateral seepage, administrative waste, on-farm ditch seepage" consumptive

use, tailwater return flow and ground water return flow. For each of these

flow volumes TDS concentrations and salt loading are either known or

calculated. The values of the many variables in these models are determined

both for pre and post project conditions utilizing field data. Many of these

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