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Show tection from floods have generally increased, prices have increased materially making in many instances early in- vestments more profitable. Some projects even with such increments in their favor, still were unable to fulfill their basic objectives. These for the most part were those which were too inadequately financed, too poorly planned, and overly ambitious. This was particularly true of numerous private irrigation and drainage worls. Unanticipated physical conditions have proved a seri- ous factor in a few cases. One of the most serious causes giving national concern to the whole problem of water resource development is sedimentation. Early investi- gations had revealed the seriousness of erosion nationally and regionally, but comparatively little attention was given this factor until recently. Sedimentation will, in time, affect the utility of many engineering works. It has filled many small reservoirs built for a variety of purposes. It has created situations which will necessitate the expenditure of large sums of money to protect the existing economy. Outstanding in this respect is the Middle Rio Grande Basin. Here, within a floodway constructed by local interests, the river bed is rising because of the inability of the stream to move its sediment load. This has resulted in a major flood and drainage problem throughout some hundred miles of river. Below the floodway and above the upper end of Elephant Butte Reservoir, sediment deposits have become over- grown with brush and small trees; the river channel has greatly deteriorated so that a swampy area thickly cov- ered with vegetation has been formed, resulting in a high nonbeneficial consumptive use of water. Now a major operation is necessary to save the Middle Rio Grande. Sedimentation is also serious on the Colorado, Pecos, and other southwestern streams. Sedimentation is also a major factor in the Los Angeles flood-control project. Here numerous small debris basins at the mouths of steep canyons are catching the products of erosion from a degrading mountain mass. Costs of re- moval of this debris are increasing from an original 5 cents to more than a dollar per cubic yard as sites in which to pile the debris are more expensive or more distant due to the encroachment of residential construction. Urban growth has had a marked effect, both bene- ficially and detrimentally, on many projects. Many flood- control projects, by reducing the volume of floods, have permitted higher use of lands. Much property in Pitts- burgh has attained a greater value. Along the rivers where levees are built, use of the flood plain is more de- sirable. On the other hand, the urban growth around Los Angeles has preempted the debris cones and increased the hazard. The construction of a large number of ex- pensive concrete lined channels, upstream reservoirs, and debris basins were required to permit safe urban develop- ment in these later hazardous areas. Some unanticipated physical conditions have proven beneficial. When the Salt River project in Arizona was inaugurated, groundwater was found at a considerable depth. However, as irrigation progressed, drainage from the project caused the groundwater to rise making it pos- sible for many to irrigate certain areas by pumping instead of from the ditch. Thus a considerable acreage of land outside of the project benefitted indirectly from the proj- ect. However, excessive pumping is increasing to the point where the groundwater has been and is being seriously lowered. Other instances of failures or of declining values in projects are in pump irrigation. Overpumping as in the San Joaquin Valley has resulted in considerable acreage of land going out of production because pumping has exceeded the replenishment. This process is also under way in the Panhandle portion of Texas, in the Gila and Salt River Valleys in Arizona, and in Las Vegas Valley in Nevada, as well as in many other areas. War needs necessitated the construction of reservoirs for low water regulation on the Mahoning River for a cooling water supply to speed up steel production. The creation of these reservoirs for that purpose has compli- cated the problem of providing sufficient flood protection in the basin. Other types of physical factors affecting the success of projects include inadequate investigations and interpre- tations of geological conditions of foundations, such as water soluble material, or highly permeable gravels, prior to start of construction. These inadequacies in the design of a few projects in the past have shown the need for acquiring services of competent geologists and engineers to ascertain the suitability of foundations in the planning stage. Political considerations have adversely affected some projects. For example, the Tallahatchie-Yazoo water- shed flood control project in northern Mississippi involved the public acquisition of worn-out and badly eroded farms, and the submarginal and poorly managed forest lands. This resulted in a fear that the whole area would be de- populated. As most of the loss and most of the watershed programs were in a single congressional district, the up- land watershed land treatment program was held up by State legislation. This upset the whole plan as originally conceived and brought many new problems to the fore. Another unforeseen political action was the loss of "Emergency" help to the Wheeler-Case irrigation projects. In these projects relief labor was to be used as a subsidy to help projects get on their feet, physically and financially. The loss of this relief subsidy for some of the projects put them out of commission. The treaty of 1906 with Mexico which required de- livery of 60,000 acre-feet of water annually to Mexico made necessary the construction of the Elephant Butte Dam, the main reservoir of the Rio Grande project. Negotiations with Canada concerning the waters of Milk River materially affected the amount of water available for the Milk River project as originally planned, and for which the works were partly constructed. Conflicts with Mexico had much to do with the development of the Ail-American Canal. A recent decision of the West Virginia Supreme Court to the effect that the State could not abrogate its police functions nor commit future legislature to make expendi- tures, would practically nullify the Ohio River Valley Water Sanitation Compact, and if supported by the United States Supreme Court, will throw doubt on the effective- ness of desirable State compacts. Both benefits and damages develop from the changing of the Colorado River below Hoover Dam from a muddy stream of irregular discharge to a clear, regulated river. Most of the damages arising from deposits of sediment downstream at the head of Lake Havasu and the reservior 406 |
