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1 - , It Chapter 1 Supplemental Water A. SUPPLEMENTAL WATER DEFINED Supplemental water IS addlllonal water provided 10 supply that which IS lacking, i.e.. needed or desired Because water IS unevenly dlstnbuled In time and space, storage and transportation are the key elements In any strategy to provide supplemental water. In this study. supplemental water is conSidered 10 be water which 15 made available lor use within a specific area by moving It from one area to another and/or sloring II for use at a later time. Supplemental water can be provided by constructing surface-water reservOirs, by adding to groundwater storage and by Importing groundwater or surface water from another area, . The objective of prOviding supplemental water IS 10 balance the supply Irom available sources for the vanous uses. The concepl of supplementing a local limited water supply is as old as civllizallon. The practices of adding storage to enhance or augment water supply Irom another source are equally old Knowledge and technology. however, surely limited human habitation to environs near surface-water supplies from streams. ... ~ p' '" '^ / , l^ J .~ l 'YV lakes. and springs. Gourds and fabricated containers permilled excurSions, not relocation of people. The needs to capture and supplement a given supply through storage undoubtedly led to the digging or enlargement of depressions to calch and hold rain and the constructIon of primitive rock or earthen dams across small streams. The first direct use of the ground- water reservoIr as a sole source of water supply or as a supplement to a surface supply probably was from hand-dug shallow holes In dry stream beds. Technology limited Ihe use of storage in either surface structures or from groundwater reservoirs until historical times. B. SOURCES OF SUPPLEMENTAL WATER ThiS report considers a variety of sources and methOds for supplemenllOg water supplies. Those which were considered 10 the study period, but not in- cluded In delall in thiS report. deserve some discussion here. These include using the SOil profile as a water source and a location for supplemental storage through conservation practices. reduction 01 evapotranspiration. weather modifIcation and reduction of losses from sur- face water. One source of water is that contained within the soil proWe. The soil zone. depth from the surface of two 10 flve feel. is a type of storage reservoir. The supply vanes depending upon characteristics of the SOil, time and amount of precipitation, and other climatic factors affecting evaporation or plant transpiration. Various conservation methods have been used to supplement or Increase the supply of water in the soil profile. Land- treatment practices such as contour plowing. terracing. mulching. and ecofallow prOVide supplemental water by Increasing the available soil moisture for plants. These practIces. along with land shaping and leveling, also contnbute to groundwater recharge, Quantltying the amounts of supplemental water provided by these methods IS difficult. likeWise II IS dlfficullto measure Not conSidered to be supplemental water are natural stream flow that IS dlVerted 10 "panan land and groundwater used wlthlO one mde of the potnt of withdrawal. ,.,