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<br /><, <br />! '- <br /> <br />r~ <br />(", <br />.,...oj <br /> <br />The two radio telemetry weather stations located on the east and west <br />ends of the Grand Valley measured the cl imatic parameters needed to <br />calculate potential evapotranspiration (ETp). The weather data for <br />calculations of ET data were transmitted directly to the Grand <br />Junction field office every 15 to 20 minutes from the two weather <br />stations. These data were stored in the computer for later use. <br /> <br />Crop consumptive use for each crop was determined using the Modified <br />Penman equation developed by Agricultural Research Service (ARS), Fort <br />Coil ins, Colorado. The crop coefficient curves for ET calculations <br />were developed by the SCS, ARS and the Cooperative Extension office <br />located in Grand Junction. <br /> <br />SITE SELECTION <br /> <br />Sites have been selected to represent the general conditions in the <br />Grand Va II ey with regard to crops, so i Is, i rr i gat i on systems and <br />management practices. A number of criteria has been establ ished for <br />the site selection process. Some of the major ones include: <br />monitoring sites must be isolated from other fields, inflow weir <br />should not be close to the headgate, water source for inflow must be <br />independent, and tai Iwater from outflow must be isolated so that water <br />from other sources does not get mixed in. <br /> <br />A monitoring site is defined as a single field or a fixed portion of a <br />field, that is irrigated as a single irrigation set or a series of <br />sets. A site has a fixed size throughout the irrigation season. <br /> <br />EQUIPMENT SET-UP <br /> <br />There were some equipment malfunctions in 1990. However, because of <br />extra equipment on-hand, the fai led equipment was replaced without <br />loss of data. <br /> <br />The f I oat sensors us i ng potent i ometers were i nsta I I ed at severa I sites <br />with outflow weirs to measure the volume of water leaving the fields. <br />These float sensors were connected to Easy Logger field units for data <br />recording and storage. The sti II ing wells (pot chambers) for some <br />float sensors experienced si Itation. This problem was controlled by <br />regular removal of si It from the sti II ing wells during routine site <br />check. <br /> <br />Most of the inflow sites under surface irrigation had Drexelbrook <br />linear gauges for measurement of inflow volume to the fields. These <br />gauges were connected to Datapods for data recording and storage. <br />Site 18 has an underground pipel ine del ivery system monitored with a <br />magnetic flow sensor. This equipment measures the amount of water <br />be i ng supp lied to the fie I d and the Easy Logger records and stores the <br />measured data. <br /> <br />10 <br />