Summary of Monitoring and Research Cottonwood Ranch

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t Explanation of Equipment and Training Costs Included in Attached Table: The Survey is rapidly moving to hydroacoustic technology for measuring streamflow, and both the equipment purchase and the training axe related to tliis change. There are several advantages to using hydroacoustics for streamflow measurements civer conventional mechanical current meters that are very beneficial far the work at Cottonwood Ranch, including more accurate and faster measurements, increased safety, and. value-added data. The handheld Acoustic Doppler Velocimeter (ADV) will be used for wading measurements; it replaces both the small pygmy and the larger AA Price meters. This is very useful for a stream like the Platte which can have long stretches of very shallow water, where it is best to use the pygmy meter, and yet can have deeper sections where the AA meter is best suited. The ADV is equiped with an electronic data logger that eliminates potential transcription errors and speeds the measuring process, which is important when flows are changing. The ADV is the same type of equipment that has been used by Paul Kinzel for his work at Cottonwood Ranch. Because of its location far from any bridges, measuring streamflow above wading stage at Cottonwood Ranch will require the use of a boat. Using; a conventional AA cunent meter attached to a weight suspended from the boat requires tlaat a cable be stretched across the channel for the boat to attach to. The boat is held in position while the depth is determined and the velocity readings are taken. This can create a seriou;s safety issue when debris is flowing down the river. Using a boat mounted acoustic Doppler current profiler (ADCP) eliminates the need to stretch a cable and hold the boat in a set positio:n because the measurement is made while the boat is moving. Besides being much faster and safer•, the ADCP also determines the velocity vectors (speed and direction) throughout most of the cross-section rather than at a relatively few points as in a standard AA current-meter measurement. Research is also underway to relate the backscatter readings from the ADCP to sediment concentration in the flow. Such value-added data would be especially useful for any study of sediment transport. The speed with which ADCP measurements can be made would also enable much beitter data to be collected during any natural or artificial high-flow events flows when flow rates cou.ld be changing rapidly. All this leads to the reason for ADCP training. Part of the budget for Cottonwood Ranch was for the measurement of high flows. Because there have been no high flows to measure, due to the drought, funds were avaiable for ADCP training that wi.ll allow for better data to be collected in the future, when higher flows eventually come. The training is a USGS requirement before ADCP measurements can be made. No one in the District had the training at the time. Having two people with the training increases our flexibility in responding to unplanned high-flow events. Phil Soenksen Chief, Hydrologic Data Section Nebraska District, U.S. Geological Survey 402-437-5156 pi soenks(a),uss.,gov http://ne.water.us.izs.gov 7