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CHAPTER I
INTRODUCTION
BACKGROUND
Today, water in the west and in the state of Wyoming is a scarce resource, a resource which must be accounted for and conserved. Water in Wyoming has many uses, including: recreation, wildlife habitat, power generation, municipal, domestic and agricultural. With so many uses placed upon Wyoming's water, it becomes obvious that there is a real need for an accurate accounting of this precious resource.
Water in the State of Wyoming is accounted for by several means. Measuring mountain snowpack, water removed from groundwater wells or the quantity of water a given residence uses every month are a few of these means. One important process which continues to require accurate measurement and research is conveyance loss.
At its simplest, conveyance loss refers to the amount of water a stream or canal naturally loses in being conveyed between two points along its course. Conveyance loss is crucial to all appropriators. Most appropriators, including farmers and ranchers, need an accurate accounting of conveyance loss especially if they have rights in a reservoir. This is because they need to know how much total water to order from the reservoir (amount of water needed at the farm or ranch plus the conveyance loss amount).
There are many factors affecting conveyance losses in streams or canals. Pahl (1985)
presents the following list of possible causes for conveyance loss:
Length of reach,
Natural flow of the river,
Size of increase in flow,
Precipitation,
Elevation and slope of water table,
Stream channel characteristics,
Silt layer characteristics,
Evaporation,
Evapotranspiration,
Hydraulic characteristics of the aquifer,
Irrigation return flows,
Diversions, and
Valley cross sections.
Until recently, the methods most commonly used to determine conveyance losses of a stream or river were based on a water budget analysis. The concept of a water budget analysis is that the difference between the flow of water into a reach and the flow of water out of the same reach is the conveyance loss. The major drawback to this method of analysis is that a stable flow period over a long time interval is required (Hanlin 1988). Today, however, computer models are available which estimate conveyance losses without the requirement of a stable flow period. One such model is the J349 conveyance loss model (Farber 1992).
Farber obtained the source code for the J349 computer model from the United States Geological Survey (USGS) and modified the code so that it would run on a 286 or higher personal computer. Farber applied streamflow data collected by Pahl (1985) and Hanlin (1988) to the model. In his thesis, Farber concludes that the J349 model is capable of modelling actual streamflow data and would provide reasonable estimates of conveyance losses.
PURPOSE AND OBJECTIVES
The purpose of this research is to apply the J349 model to streamflow data collected on reaches of the Greybull and Wind Rivers to accurately estimate conveyance losses in these reaches. The results of this modelling will help local water commissioners, hydrographers and water appropriators to properly quantify conveyance losses. Appropriators will then be able to more accurately release the correct amount of water from storage. The objectives to accomplish the above purpose are:
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