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CHAPTER VI
CONCLUSIONS AND RECOMMENDATIONS
CONCLUSIONS
The results of the research presented in this paper and research conducted by Farber(1992), Hanlin(1988) and Pahl(1985) are the basis for the following conclusions.
First, the J349 hydrologic computer model was able to accurately simulate fluctuations in stream stage. However the model predicted flows lower than actually existed during high flowrate periods and predicted higher flow values than actually existed during low flowrate periods. This trend is also observed in research conducted by Farber (1992). These results show that the J349 model is able to reliably simulate flow changes in the range of 200 to 400 cfs. In areas where flows deviate by more than 300 cfs, the model loses some accuracy in simulating actual flowrates. Using the J349 model to determine conveyance loss on reaches where streamflow data has high variability was beyond the scope of this study.
Secondly, the J349 model produced conveyance loss estimates on the Greybull River between Meeteetsee and the Farmers and Bench Canals which are reasonable and realistic when compared with other streams in Wyoming utilized by Pahl (1985) and Hanlin (1988). Hydrographers and others should be able to use Figure 12 provided in this thesis to determine incremental conveyance losses to be assessed downstream users for any arbitrary increase in flow between 50 and 1950 cfs. However, the results produced by the model are most accurate for flows ranging between 300 and 600 cfs.
Verification of data collected from outside agencies is essential. All sources and diversions within the reach under consideration must be accounted for in order to use the J349 model to the best of its ability. An accurate accounting of wastewater flow from canals and ditches reentering the river within the study reach is key to making the J349 model simulate actual flows.
The J349 model is very sensitive to increases in transmissivity and storativity. Small changes in these variables resulted in large changes in predicted downstream flow values calculated by the model. Changes in these variables in either direction also made a marked difference in conveyance loss calculated by the model. When storativity and transmissivity were increased, the conveyance loss calculated by the model also increased.
RECOMMENDATIONS
First, it is recommended that a visual survey of any reach be conducted before any streamflow data is collected where conveyances losses are to be estimated. A visual survey would provide valuable knowledge of the flow data that would be required to be collected to make the J349 model function correctly. A visual survey would also allow for a better understanding of aquifer characteristics in the area under consideration.
Secondly, it is recommended that storage and groundwater/surface water interactions present in the model be altered so that actual flowrates with high variation can be more accurately simulated. The J349 model should also be modified to allow for more than 25 changes in diversion values during the time period to be modelled.
Since transmissivity and storativity have such a great influence on the results determined by the computer model, a more accurate estimate of these parameters is needed. Well tests could be performed near the river to better define these aquifer characteristics.
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