Continued Operation of a Raingage Network for the Imperial Valley Water Authority Year Two: September 1993 - August 1994

Regional precipitation viability affects irrigation water demand on an aquifer, aquifer recharge, and the density of wells and irrigation systems required for agriculture and water supplies. These factors all affect any required water withdrawal allocations from an aquifer. Therefore, knowledge of the precipitation variability over an extensively irrigated region, such as the area within the Imperial Valley Water Authority (IVWA), should provide useful information for the management of ground-water resources in that region. The Illinois State Water Survey (ISWS) has a long-term interest in precipitation measurement and related research. For the past 40 years, the ISWS has operated raingage networks over various time periods in both rural and urban areas. An agreement was reached between the IVWA and the ISWS in spring 1992, and a 25-site network was established in late August 1992. This report documents network operation, maintenance, data reduction, and management during the second year of operation (September 1993-August 1994). This report provides data analyses for the year. Several appendices also document actual raingage sites, instructions for raingage technicians, raingage maintenance information, large precipitation amounts recorded during the year, and monthly precipitation variability at each site. Data collected during the somewhat drier 12-month period served as a useful contrast to the record-breaking amounts of precipitation measured during the network's first operational year. The exposure and areal coverage of the network still seem to be adequate to capture the precipitation variability of the region. Because of the relatively dense raingage spacing, the network also is providing high-quality data for research purposes. After data are collected from a third year of network operation, a matrix of correlations of precipitation amounts between raingage sites will be constructed to identify regions of spatial coherency in the precipitation-producing systems traversing the region, allowing further assessment of the spatial variability of the precipitation. Estimates of the probabilities of different storm paths and precipitation patterns in the area also should be possible because these types of statistics become more stable as the sample size of the database increases. These data and statistics, in combination with ground-water information now being collected in the area on a routine basis, should enhance the ability of the IVWA to accurately and efficiently manage the region's underground water resources.Imperial Valley Water AuthorityOpe

Continued Operation of a Raingage Network for the Imperial Valley Water Authority Year Three: September 1994 - August 1995

Regional precipitation variability affects irrigation water demand on an aquifer, aquifer recharge, and the density of wells and irrigation systems required for agriculture and water supplies. These factors all affect any required water withdrawal allocation from an aquifer. Therefore, knowledge of the precipitation variability over an extensively irrigated region, such as the area within the Imperial Valley Water Authority (IVWA), should provide useful information for the management of ground-water resources in that region. The Illinois State Water Survey (ISWS) has a long-term interest in precipitation measurement and related research. For the past 40 years, the ISWS has operated raingage networks over various time periods in both rural and urban areas. An agreement was reached between the IVWA and the ISWS in spring 1992, and a 25-site network was established in late August 1992. This report documents network operation, maintenance, data reduction and analysis, and management during the third year of operation (September 1994-August 1995). Data showing the differences among the first three years of operation are included. Several appendices also document actual raingage sites, instructions for raingage technicians, raingage maintenance information, unusually large precipitation events recorded during the year, monthly precipitation variability at each site, and total rainfall during each storm period in the three years of network operation. The third year was the driest of the three years of operation. It had the wettest spring (March-May) and the driest winter (December-February) and summer (June-August). The third observation year had on average approximately two more rain days at each station, and an average of three more rain events per station than were observed during the second observation year. Both the second and third years had fewer rain events and rain days than during the first observation year. Because of the relatively dense raingage spacing, the network also is providing high-quality data for research purposes. Data from the first three years of observation will be analyzed during the next year to determine correlations of precipitation amounts between raingage sites and to identify regions of spatial coherency in the precipitation-producing systems traversing the region, allowing further assessment of the spatial variability of the precipitation. Estimates of the probabilities of different storm paths and precipitation patterns in the area also will be developed. These data and statistics, in combination with ground-water information now being collected in the area on a routine basis, should enhance the ability of the IVWA to accurately and efficiently manage the region's underground water resources.Imperial Valley Water AuthorityOpe

Installation and Operation of a Raingage Network for the Imperial Valley Water Authority Year One: September 1992 - August 1993

Regional precipitation viability affects irrigation water demand on an aquifer, aquifer recharge, and the density of wells and irrigation systems required for successful agriculture and water supplies. These factors all affect any required water withdrawal allocations from an aquifer. Therefore, knowledge of the precipitation variability over a highly irrigated region, such as the area within the Imperial Valley Water Authority (IVWA), should provide useful information for the management of ground-water resources in that region. The Illinois State Water Survey (ISWS) has a long-term interest in precipitation measurement and related research. For the past 40 years, the ISWS has operated raingage networks over various time periods in both rural and urban areas. An agreement was reached between the IVWA and the ISWS in spring 1992, and a 25-site network was established in late August 1992. This report documents network construction, operation, maintenance, data reduction, and management during the first year of operation (September 1992-August 1993). This report provides data analyses for the year. Several appendices also document actual raingage sites, instructions for raingage technicians, raingage maintenance information, large precipitation amounts recorded during the year, and monthly precipitation variability at each site. Data collected are providing new information about the variability of precipitation in the region. The exposure and areal coverage of the network appear to adequately capture the precipitation of the region. Because of the relatively dense raingage spacing, the network also is providing high-quality data for research purposes. After the second and third years of data collection (September 1993-August 1994 and September 1994-August 1995), matrices of correlation coefficients between each raingage site will be computed on a seasonal, yearly, and three-year basis. The correlation analysis will help identify regions of spatial coherency in the precipitation-producing systems traversing the region, allowing further assessment of the spatial variability of the precipitation. Estimates of the probabilities of different storm paths and precipitation patterns in the area also should be possible because these types of statistics become more stable as the sample size of the database increases. These data and statistics, in combination with ground-water information, should greatly enhance the ability of the IVWA to accurately and efficiently manage pumpage of water from the local aquifer.Imperial Valley Water AuthorityOpe