OCR Text |
Show The Situation A realistic judgment on essential basic data needed in the Central Valley Basin must take into account the following phases: (1) requirements for preliminary investigations, (2) requirements for purposes of general survey investigations (general coverage), (3) data requisite for definite project investigations (specific coverage), and (4) data for construction and operation (which can appropri- ately be gathered in the course of those activities). Data already available for the first and second phases have permitted the drafting of a compre- hensive plan for physical development in the Cen- tral Valley from which initial units have been selected. Likewise, data have been generally ade- quate for the detailed planning and construction of existing projects, although additional data on sur- face water conditions will be necessary for other projects as they are developed. Ground water information is less adequate. In general, the Central Valley is more adequately supplied with basic data than many other sections of the country. The long interest of the State in water programs has resulted in the accumulation of much information. However, to develop adequate plans for future specific projects the present program of data collection should be continued and expanded to insure that data will be available when needed. The Subcommittees on Hydrology and on Sedi- mentation of the Federal Inter-Agency River Basin Committee have made a survey of the desires of various action agencies for additional data for all purposes in certain general areas, and have esti- mated the adequacy of existing measuring facilities. The results of this survey for the Central Valley are shown below: Adequacy of existing TvDe of da ta • measuring facilities1 x ype or data. (range o/ percent) Precipitation---------------------------------------41- 60 Evaporation___________________________21-100 Snow courses__________________________61-100 Ground water__________________________ 6- 40 Stream gaging_________________________41- 60 Chemical water quality__________________21- 60 Sediment load_________________________ 0- 20 Reservoir sediment survey________________41- 80 1 Measured in terms of percentage of the estimated total required facilities for all purposes. Topographic maps are available for nearly the entire Central Valley Basin, but many do not con- form to modern standards. However, the present 130 and proposed 10-year mapping program under way by the Geological Survey in cooperation with Cali- fornia and the mapping program of the Forest Serv- ice meet most needs of the basin. Adequate geo- logical maps and information are available for only a small part of the basin. Some sanitation studies have been made, particu- larly by State agencies. With the increasing popu- lation and industrial growth more extensive studies will be required. Soil surveys and land classification surveys are available for practically all of the existing or poten- tial agricultural land in the basin, but generally on a reconnaissance basis. More detailed surveys either are being made or will be required in specific areas as studies of potential projects progress. A number of agencies are already engaged in research on land management problems, and this work should be maintained and increased to meet situations which are likely to become more critical in the future. A complete study of underground water storage possibilities of the upper San Joaquin Basin should be undertaken, covering the capacity of the gravels near the ground surface, as well as the deep aquifers. These aquifers should be studied with a view to replenishment, either locally or if necessary at some distance, and their source discovered. Ground water recharge is a very important aspect of water use in the Central Valley. More informa- tion is needed on most efficient methods of adding to ground water supplies. Associated with ground water recharge is the problem of leaching of alkali salt accumulations. More needs to be known as to the best means of accomplishing recharge. Maximum use of irrigation water requires more research on the time and rate of application of water for different crops, and on varying soil con- ditions, including drainage characteristics. Drain- age conditions are of particular interest in relation to the Solano Project. It is possible that more precise criteria can be developed as a guide to farmers in the valley by more detailed study of those significant factors which, collectively, determine the degree of water requirement. In addition to the crop and soil, these factors would include such things as solar radiation, humidity, and temperature. Research of this type has been undertaken for some of the valuable orchard areas in California. The potential practical value of such guides to farmers, and the possible savings in water, warrant extensive study of this subject. |