This was true in the Eloy area of Pinal County, the areas concentrated pumping in Pima and Santa Cruz Counties, and the parts of Maricopa County that depend solely on ground water for irrigation. Accelerating the decline in water levels was the waste of water by transpiration from valley-bottom vegetation. In the Gila and Salt River Basins, in Maricopa and Pinal Counties, it is estimated that this waste probably amounts to between 400,000 and 500,000 acre-feet a year, and in Safford Valley in Graham County the annual waste amounts to 70,000 acre-feet. The value of the water for irrigation is also deteriorating as its mineral content increases through concentration resulting from irrigation use.

Methods of study. The following procedure is proposed: To study each valley separately and to give each one special attention according to the nature of its groundwater problems. The valley unit is a logical subdivision in the basin and range region because each valley is a separate ground-water basin. The county unit is the logical division in the plateau region. First attention should be given to those valleys or counties in which critical ground-water problems now exist or in which waterproject developments will soon take place.

Test drilling. The character, thickness, and areal extent of the water-bearing formations can best be ascertained by drilling small test wells. These wells can often be used as permanent observation wells. For this purpose it would be desirable to purchase drilling rigs and to operate them continuously throughout the period of investigation. This method would also aid in determining the location of permeable deposits beneath the uplands as well as in the valley lowlands.

Geophysical prospecting.-The value of the test wells drilled in the above program could be greatly extended by the use of geophysical prospecting. This has already been proved in connection with the drilling of water wells for army camps in the area.

Geologic correlation.-Geologists with ground-water experience should study and correlate the samples obtained from the test wells and outcrops of the formations with the results of the geophysical probes. Such study will aid in planning further test drilling, in locating new supplies, and improving existing supplies.

Pumping tests. Pumping tests should be made wherever possible, usually on existing wells. The recent advance in pumping-test methods makes possible the determination of the water-yielding properties of formations and provides practical means for determining well spacing, quantities of water to be expected from wells of different size, draw-down of the ground-water level, interference of one well with another, amount of water derived from flow of nearby streams, local geologic conditions affecting the occurrence of ground water, and the design of well fields.

Pumpage inventory.-Records should be obtained of

the quantities of water withdrawn from wells throughout the basin in order that this information may be available for use in conjunction with studies of fluctuations of water level in determining the perennial yield of the formations. Records should be obtained from each town, irrigated area, railroad, and industrial plant, and measures should be developed for obtaining continuing records of this kind. for the future.

Water-level measurements.-In order to determine the trends of ground-water levels and the changes in groundwater storage, an enlarged program of measurements of water levels in wells should be started and periodic observations should be made. The number and location of the observation wells in each valley or county would depend upon the importance and complexity of the ground-water conditions. Some of the wells should be equipped with automatic water-stage recorders in order to obtain daily records. Other wells should be measured once a week, once a month, or only a few times a year. New observation wells should be placed in areas of heavy ground-water pumpage and in areas in which water development projects are to be made. They should be established also near dams, reservoirs, irrigation canals, and drainage ditches, in order to ascertain the effects of the operation of those structures on ground-water conditions. Observations of this kind are now being made in the Santa Cruz River Basin in Santa Cruz, Pima, and Pinal Counties, and in parts of Maricopa, Graham, and Greenlee Counties.

Depth to water level. The study should include an inventory of existing wells and the collection of information on the size, depth, and diameter of the wells, the kind and size of pump, and the use to which the water is put. Maps should be prepared where feasible, showing depths to water level.

Delimiting areas in which vegetation draws heavily on ground water.-Where ground water occurs at shallow depths, the roots of plants and trees extend to the capillary fringe or to the zone of saturation and they extract water in a manner similar to pumping from a well. It is roughly estimated that 1,000,000 acre-feet of ground water is consumed in this manner in the Lower Colorado River Basin, most of it by useless vegetation. Probably the greatest potential source of salvage of ground water lies in the reduction of use by vegetation that has little or no value; areas having such vegetation should be mapped with view to the effecting of measures for reducing the wastage of water. Some work has been done on this problem in Arizona and the results indicate a tremendous use of ground water by this type of vegetation. Salt cedar is one of the heaviest users and also one of the worst types in choking the flood channels. Along the Gila River from the Ashurst-Hayden Dam to the junction with the Salt River, more than 100,000 acre-feet of water are wasted annually by this type of growth. Similar conditions pre

vail at many other places in the basin including localities where irrigation has raised the ground-water levels and has created new areas of vigorous plant growth.

Determining water used by valley-bottom vegetation and experimental clearing.-An area would be carefully chosen where full cooperation of all interested parties could be obtained. Tests would be run on this area which would then be cleared and the salvage of water determined.

Mapping areas favorable for artificial recharge.-The building up of ground-water storage through artificial recharge from reservoirs and irrigation canals is accomplished in many places and the extension of this practice to new projects in the basin will undoubtedly augment ground-water storage. In addition, the flood flows of some of the streams could be diverted in such a manner that there would be seepage into the subterranean reservoirs where geologic conditions are favorable. Such possibilities should be mapped, especially where it may be expected to become over-developed in the future. Artificial recharge may be effected in some of the cities through recharge wells in which water is fed into the water-bearing formation during certain seasons of the year in order that it will be available for use in other seasons. The lowering of the water table along streams produces conditions favorable for artificial recharge in the sense that seepage is then induced from the streams into the subterranean reservoirs. The location of well fields near streams to take advantage of this source of water, including the filtering action of the sands and gravels and the more uniform temperature of the ground water, will undoubtedly prove to be the most logical solution for many watersupply problems of the basin. The ground-water study of the basin would include the mapping of stretches of the stream valleys that are favorable for this kind of groundwater development.

Interpretation of data and preparation of reports.— The data gathered in the field studies should be interpreted by competent engineers and geologists, and both the data and the interpretation should be presented in comprehensive reports. These reports should constitute an inventory of the ground-water resources of the Lower Colorado River Basin. They should form a reference library of information on the subject that would be invaluable in future planning for all kinds of water development. The interpretation of the data would be directed toward specifying new sources of supply for cities, railroads, farms, industries, and irrigation, determining the safe yield of developed areas, and methods of improving the present supplies.

Estimates of cost.-The collection of the data, the interpretation of these data, and the preparation of the reports should be carried on simultaneously, in large part by the same group of geologists and engineers. It does not appear practical, therefore, to estimate the total cost

of the comprehensive study on the basis of individual items. Moreover, the annual cost of the study would depend upon the number of valleys or counties in which investigations were made each year. The experience of the Geological Survey indicates that studies made in the detail outlined above would require an average annual expenditure of about $125,000 with the addition of $50,000 the second year to cover the cost of a clearing project.

QUALITY OF Water

There are two aspects of the quality-of-water problems in the Lower Colorado River Basin, namely: (1) The quality of the waters now available in surface- and ground-water sources, and (2) the quality of the water in surface sources that will be available after further development of irrigation in the upper basin and after diversions have been made from the headwaters into other drainage basins. By the withdrawal of water of good quality, these diversions will deteriorate the quality of the water in the streams below the diversions. Utilization of water for irrigation and other purposes will also cause changes in the quality of the water. The evaporation of large volumes of water stored in reservoirs and the resulting concentration of dissolved solids will obviously deteriorate the quality of the water that remains. Water utilization in the headwaters that causes changes in the chemical character of a river water will have an effect on the quality of water available below the headwaters, and the effect may be noticeable at the lower end of the lower basin.

Sediment records are needed for several streams in the lower basin, and the sediment records obtained for streams in the upper basin will be of value in planning for utilization of existing and new reservoirs in the lower basin.

Brief descriptions of quality-of-water and sediment studies that should be made are given in the following paragraphs:

Quality of water for industrial and agricultural purposes. It is desirable to have information on the changes in concentration and character of waters that are potential sources of industrial and municipal supplies. The requirements for industries are rigid, and complete information on the quality of the available supplies is needed in making plans for industrial uses. The value of a water supply for industrial purposes may be seriously impaired because of previous uses to which the water has been put, especially when the source may be contaminated because of such uses. The comprehensive records proposed for this study will give the data necessary to determine the usefulness for most industrial purposes.

The quality of a water for irrigation uses is dependent on the nature and the amount of the dissolved constituents

in the applied water, and on the amount of dissolved solids that are carried by the drainage from the irrigated Studies must, therefore, include the determination

area.

of the concentration and chemical character of both the waters used in irrigation and those in the drainage ditches. For the computation of quantities of dissolved solids carried to and removed from an irrigated area, it is necessary to have adequate stream-gaging records and all samples must be collected at points where stream-flow records are available.

In the Lower Colorado River Basin, information is needed on the quality of available ground-water supplies. In irrigated areas, it will be necessary to collect samples of the normal ground waters and also of the drainage waters. For most of these sources, one complete analysis and partial analysis of three to twelve samples a year will be needed to give the desired information. For surface water sources, it will be necessary to have daily samples on which one or more determinations will be made for showing change in concentration. As a rule, the samples for ten consecutive days will be made into a composite sample for a complete analysis.

The proposed quality-of-water studies will include the analysis of samples from reservoirs for the purpose of studying changes that may take place during storage. Because of the high rates of evaporation in the lower basin, there are appreciable changes in concentration and chemical character during storage, but records of these changes are meager.

The estimated cost of the quality-of-water studies in the Lower Colorado River Basin, including the quality studies in irrigated areas, quality studies in reservoirs, equipping of the laboratory, field work, and analyses of the samples, will amount to $44,000 for the first year and $35,000 for each subsequent year. It is likely that the existing gaging stations will be satisfactory for the sampling program and no new stations will be needed.

Sediment transportation.-Sediment studies have been carried on for a number of years at the Lees Ferry, Grand Canyon, and Yuma gaging stations on the main river. Prior to the closing of Boulder Dam, samples were collected at the Topock and Willow Beach gaging stations. The records for Lees Ferry and Grand Canyon should be continued, and sampling points should be established in the Little Colorado, Paria, Virgin, and Williams Basins. In addition, studies should be made to determine the nature and rate of sedimentation along the course of the river and in reservoirs. Such studies would be in the nature of a reconnaissance and would not duplicate the work done in a comprehensive sedimentation survey of the existing reservoirs. The estimated cost of the sediment studies, including the collection of samples, equipment, field and laboratory work, is $60,000 for the first year, and $50,000 for each subsequent year.

WATER UTILIZATION

In addition to the collection of basic information concerning stream flow, ground waters, and the quality of both, the water program of the Geological Survey embraces special compilations or arrangements of these data for purposes of general utility and the interpretation of the data, as well as other related physical and economic information.

Compilation of water facts.-An essential item of the program for the Lower Colorado River Basin is the collection of comprehensive water information pertaining to the quantity and quality of surface and ground waters, the status of their utilization, and the publication of such information in reports of convenient form for use and reference. The reports would present data regarding storage, diversion, and types of water use. The inclusion of a series of monthly charts of the Lower Colorado River Basin and adjoining areas showing in detail the relation between monthly and normal stream flow, would be useful in evaluating or expanding short or broken stream-flow records. The reports would give authoritative historical and other data concerning floods and droughts that would be helpful in the consideration of problems of natural flow and possible influences of climatic oscillations and changes wrought by man. Such information is a primary need in the adjudication of the conflicting interests of the political subdivisions and various industries now or propectively involved in the utilization of the limited water resources of the Lower Colorado River Basin. It is also needed for determining the availability and suitability of the water supply for various industries and activities that may be considered for establishment in the basin.

Interpretation of water facts.-Statistical records pertaining to water often require supplemental analysis or treatment in order to reveal their significance. The form of the analysis depends largely on the nature of the problem at hand, but it has been found that certain kinds of analyses enter into nearly every water-supply problem, and indeed, the availability of such basic analysis may encour age, or hold to wise limits, as the case may be, the application of the records to the solution of water problems.

"Deficiencies in Hydrologic Research," published by the National Resources Planning Board in 1940, describes the great number of needed investigations, some of which have singular bearing on the surface-water hydrology of the Lower Colorado River. Much fundamental work needs to be done in the Southwest and only the most preliminary or basic treatments are planned. The most general types of study that can be undertaken are statistical and inventorial.

A study of trends in precipitation, temperature, and run-off is included among the statistical investigations planned. Trend graphs shown in Water Supply Paper 772, reveal an irregular though marked downward trend

in precipitation and an upward trend in temperature over most of the country. This combination produced a substantial reduction in run-off during the period of record then available. These analyses should be brought up to date, expanded, and examined more in detail with particular emphasis on the Lower Colorado River and with such reference to tree-ring chronology or other possible ways of extending knowledge of climatic behavior as may seem applicable or prudent.

In addition to statistical analyses, a great many facts regarding the water resources can be gained from the preparation of a quantitative hydrologic inventory. Such studies consider water in streams not by itself, but as one phase in a cycle containing other intimately related phases and factors including precipitation, interception by vegetation, infiltration, soil moisture, run-off from surface and ground sources, surface and ground storage, evaporation, and tranpiration. The information developed is useful in many kinds of water problems, particularly in administration of land use and conservation programs, and in flood control. Moreover, it can serve as a basis for estimating stream flow in areas where no gaging-station records are available, and as a supplemental method in combination with rainfall records for the synthesis and extension of stream-flow records, especially through critical period of drought or flood.

The technique for the preparation of an inventory as outlined above is available but must be modified by the adequacy of the data on hand as well as by the hydrologic conditions peculiar to the basis under examination.

Water for stock use. As in the upper basin, stock raising is one of the major industries in the Lower Colorado River Basin. Vast areas of grazing lands are administered by the Grazing Service and the Office of Indian Affairs. The usable forage crop is dependent upon available stock watering places; forage on lands remote from water is unused whereas that on lands near water is overgrazed, often to the extent of accelerating destructive erosion of the soil mantle. Numerous and properly spaced range water supplies are necessary in areas now unused in order that overgrazed areas may be relieved and given opportunity for recovery.

Information and advice about water supplies on the public range is supplied by the Geological Survey for use by the Grazing Service, Office of Indian Affairs, and other land management agencies of the Department of the Interior. However, the extremely limited facilities of the Survey have prevented it from keeping abreast of current requests for advice on water supplies, and in some instances developments have been undertaken without benefit of competent geologic investigation. It is anticipated by the agencies administering the public range that the urgent need for water-development projects for stock use will greatly increase after the war.

In order to supplement well-water supplies and to open up new areas where it appears impractical or impossible to obtain water from wells, stock-watering tanks are constructed on washes and intermittent stream courses to catch some of the "flash" run-off. Virtually no hydrologic data are available for water courses of this type, and specially designed stream gages for obtaining such data are an item in the water program of the Survey. Evaporation and seepage losses are studied by means of staff gages installed in tanks at strategic sites. Weather data from nearby Weather Bureau stations are analyzed and correlated with all water information obtainable for the region under study and basic data are thus obtained for design of stock-watering tanks with reasonable assurance of successful performance and long life.

Accelerated erosion is an important problem in the lower basin. Deep gullies are trenching many valleys and draining the ground-water level below the reach of plant roots, making valueless large tracts that formerly produced excellent forage crops, and producing vast amounts of silt that became a troublesome problem to reservoirs, irrigation canals, and farms. The collection of factual information on this subject and recommendation of remedial measures is contemplated in the Survey program.

NATIONAL PARK SERVICE

The forthcoming report of the National Park Service, Recreational Resources of the Colorado River Basin, will cover this subject in more detail and will supplement the material contained herein.

The National Park Service is primarily a conservation and recreation agency performing functions which are an integral part of a program of land use of the Department of the Interior. The prime function of the Service is the administration of the National Park and Monument System. The Service seeks to preserve and render available to the public outstanding scenic, scientific, historic and prehistoric areas of national importance. The act of June 23, 1936, "authorized and directed the Secretary of the Interior to cause the National Park Service to make a comprehensive study, other than on lands under the jurisdiction of the Department of Agriculture, of the public park, parkway and recreational area programs of the United States, and of the several states and political subdivisions thereof, and of the lands throughout the United States which are or may be chiefly valuable as such areas . . The said study shall be such as, in the judgment of the Secretary will provide data helpful in developing a plan for coordinated and adequate public

park, parkway and recreational area facilities for the people of the United States."

With this responsibility and the fact that several areas in the National Park and Monument System would be directly affected by certain water-control possibilities being considered by the Bureau of Reclamation, it was determined that the National Park Service should investigate and furnish the Bureau with essential facts basic to the establishment of Departmental policy regarding the classification, development and administration of possible water-control projects and related areas in the basin, in which recreation is or will become an important dominant or collateral resource. On January 27, 1941, Secretary Ickes approved the proposal of the National Park Service and the Bureau for including a basin-wide recreational survey as a part of the studies and investigations for the formulation of a comprehensive plan of utilization of the waters of the entire Colorado River system.

Colorado River Basin Water Utilization Program and its Effect on Recreation

From Gannett Peak in the Wind River Mountains, highest point in Wyoming, elevation 13,785, Milner Pass in Rocky Mountain National Park, and the 14,000-foot mountain peaks in southwestern Colorado to the Salton Sea, 241 feet below sea level, stretches a vast region of forests, deserts, plains, mountains, canyons, and plateaus. The Colorado River Basin is one of the most outstanding recreational regions in the United States, because of great variety of natural scenery, climatic conditions, and areas and objects of scientific interest, its early romantic history, archeological background, and present Indian, Spanish, and Anglo cultures.

Here is the world's greatest canyon, the largest natural bridge, the largest man-made lake, and the highest dam. Here, too, one may enjoy the largest percentage of possible sunshine of any place in the United States and find perfect climates for outdoor recreation the year around. Hunting, fishing, photography, snow sports, boating, swimming, horseback riding, camping, mountain climbing, exploration, the entire realm of outdoor recreational activities may be enjoyed. Five national parks and 28 national monuments have been established within the basin to preserve some of the most outstanding natural, scientific, and cultural features. Large sections have been included in national forests, wildlife refuges, and grazing districts, and vast areas set aside as Indian reservations. Much of the basin is in public ownership, but this is not surprising when one sees the country and knows that about half the basin has a population of less than 2 people per square mile, and that the most densely populated county, Maricopa County, in which Phoenix, the largest city is located, has a population of only 20.2 people per square

mile.

It is only natural in a region so endowed that recreation should become one of the major industries. Agriculture is restricted almost entirely to irrigated sections. Mining, lumbering, and the raising of cattle and sheep first attracted settlers to the basin, but the recreational features are now attracting many more; and as the various sections of the basin become better known and more accessible to the densely populated regions of the United States through improved highways and air transportation, catering to the recreational business should become a major industry. To foster this industry it must be recognized that recreational use of land may in certain places be the highest or best use of the land for the general welfare of the people in the basin, and in vast sections of the basin should be on an equal basis with other uses, such as grazing or produc-, tion of timber. One of the most important recreational features of the basin is the great stretches of open range, unobstructed by buildings, fences, transmission lines, and other signs of modern civilization. As other sections of the United States become more and more highly developed, this one feature of the Colorado River country, if preserved, will have unusual appeal.

The major portion of the basin is desert or semidesert. Here water is the most precious single item. The life of the region is dependent upon the wise use of the streams and ground water. In the development of the water, recreational use should be considered along with other uses, such as irrigation, power, municipal water supply. In the mountains and high plateau sections of the Colorado Basin the clear, cold streams and lakes offer excellent fishing, amid delightful surroundings, and in some instances the recreational value of these streams and lakes may be such as to make this their most important use. In other sections the construction of dams for irrigation or power create new water areas of recreational importance, for example: Lake Mead, which has been called the "Eden of all bass fishermen," is famous throughout the country for its scenic beauty. There are also instances where the raising of water behind dams would submerge areas of scenic and scientific value or archeological importance. In such cases it must be decided whether a reservoir in that location is more or less desirable than the preservation of these existing features. If in the case of existing archeological features the decision is in favor of the reservoirs, there should be a thorough survey and excavation where found desirable, so that knowledge of the archeological material will not be lost forever. In the larger proposed reservoir areas surveys should also be made of the flora and fauna and records kept of the original biota.

The importance of recreational resources in the basin is recognized by the Bureau of Reclamation in planning for water conservation projects. Through a cooperative agreement with the National Park Service, the latter is carrying on a general survey of the recreational resources