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. ( .. ~ ( l - 14 - . Of the privately-owned rangelands in the watershed, 650 acres lie above the High ,Line Canal, and 580 acres are below. These lands are mostly in small tracts. They generally have flatter slopes, and erosion is not as serious a problem as on the Federal rangelands. The principal' land treatment measure to be applied over a three-year period is- proper range use':. .Continuanceof this practice will assure improvement, protection, and maintenance of vegetative cover. On the 1,260 acres of privately-owned irrigated cropland, an accelerated three-year program is proposed for: (1) the establishment of such practices as improved water application~ crop residue use, and fertilizing; and (2) the installation of conservation cropping systems, pasture planting, land leveling, ditch lining, irrigation pipelines, open ditch structures, and tile drains. These mea~ures are essential for the continued successful conservation operation of the land and ~nll improve forage stands and crop production, as well as reduce local runoff and sediment production. On-site benefits from land treatment measures .on privately- owned lands were not claimed for project justification (Table 1). The quantities of land treatment planned for installation during the project period by the Bureau of Land Management and by the owners or operators of private lands are shown ill Table 1. The total estimated cost of planning and installing these measures is $93,130. . Figure 2 shows the enduring type of land treatment measures to be installed on Federal lands by the Bureau of Land Management. Structural Measures for Flood Prevention This work plan proposes the installation of one floodwater- retarding structure (IW-l) on Indian Wash at a point about two miles upstream from the High Line Canal (Figure 4). It will be located on desert rangeland mostly under Federal ownership. This structure in combination with the controlling effects of the High Line Canal and the existing Indian Wash channel will afford an adequate level of flood protection to the area now subject to d~nage. The proposed floodwater-retarding structure will control runoff fram 6.53 square miles or nearly 64 per cent of the flood-producing area above the High Line Canal. The structure will provide floodwater detention storage for three inches of runoff from the area controlled. This provides enough capacity to control the runoff fram stor.m rainfall intensities greater than the IOO-year frequency stor.m event. .