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Show Chapter 1 Introduction As demand for water increases, more efficient management of both surface and groundwater resources is needed. Historically, much effort has been directed towards the design and management of surface water reservoirs. By comparison, relatively little effort has been directed at the systematic management of the groundwater resource. Also most groundwater management studies have not explicitly considered important factors like water rights, water quality and interactions with surface water. Traditionally water agencies with ample surface and ground water resources use mostly surface water during wet periods and increase groundwater use during droughts. Optimal management policies for this transition are not well defined. Groundwater use is increased as needed during the drought to make up the deficit from surface water. In this process, it is possible to have extreme drawdowns of piezometric head at some wells, and to adversely affect groundwater quality. Several water supply agencies may also infringe on each others water rights through excessive pumping during these periods. While a number of groundwater management models have been developed for the management of groundwater use for irrigation and agrarian use, very few have focused on the management of groundwater supplies in a metropolitan area where a number of water supply agencies supply relatively distinct areas from a common or connected aquifer system. Salt Lake County is a metropolitan area supplied by a number of water supply agencies, where well interference across agency boundaries is of interest. Ideally surface and ground water should be managed conjunctively. This implies that management models should simultaneously solve for surface and groundwater use for each time period. However, given the operating structure and operation constraints for most water supply agencies, this is not always possible. Flexibility in operation is often limited by the nature of surface water contracts. As an example, the Salt Lake County Water Conservancy District has a long term contract for purchasing 400 acre- feet per month of surface water from other agencies. The terms of this contract curtail the degree to which optimal rates of ground water and surface water use may be determined. Contracts of this nature have direct implications on the degree of groundwater exploitation and reservoir development, as well as on the conjunctive operation of the total water resource system. This study focused on the development of procedures for the formal analysis of long term surface and groundwater development in a metropolitan setting where independent water supply agencies compete for the resource. Mathematical optimization models that are ' practical' ( cognizant of the issues in the Salt Lake County area) were developed and exemplified with local ground and surface water data. In particular models were developed and applied for ( 1) screening candidate reservoir sites with multiple uses considered, ( 2) determining the optimal aquifer yield considering water rights and water quality, ( 3) determining least cost groundwater management strategies considering water rights, water quality and demand variability, ( 4) reservoir system operation under specified reliability rules, ( 5) screening reservoir and groundwater development under specified operation rules, and ( 6) determining the tradeoff in surface and groundwater use over critical drought periods. The emphasis of the study was on the analysis of typical issues in long term, local water resources planning and development, rather than on short term ( or within one year) operation of an existing system. With respect to the Salt Lake County applications, the perspective adopted was closest to that of a central regulatory agency. Factors presumed relevant to local water supply agencies were also addressed. It was determined that 1 |