ON THE ECONOMIC IMPACT OF LARGE DIVERSIONS OF SNAKE RIVER WATERS1

ABSTRACT. This work evaluates the economic losses due to diversion from the Snake River during the relatively low-flow year May 1928-April 1929. The results determine the losses due to pollution abatement and power generation for several different patterns and volumes of diversion, and the tool of analysis is dynamic programming.     

COMPARISON OF BANK EROSION AT VEGETATED AND NON-VEGETATED CHANNEL BENDS1

ABSTRACT: Following major floods in 1990 which resulted in widespread bank erosion in southern British Columbia, four streams typical of the region were evaluated for the effect which riparian vegetation played in reducing erosion. A total of 748 bends in the four stream reaches were assessed by comparing pre- and post-flood aerial photography. Bends without riparian vegetation were found to be nearly five times as likely as vegetated bends to have undergone detectable erosion during the flood events. Major bank erosion was 30 times more prevalent on non-vegetated bends as on vegetated bends. The likelihood of erosion on semi-vegetated bends was between that of the vegetated and non-vegetated categories of bends.     

ON LARGE DIVERSIONS FROM THE NORTHWEST – NORMAL AND HIGH-FLOW YEARS1

ABSTRACT This work assesses economic losses due to diversion of Snake and Columbia river waters in low, normal, and high-flow years, using a seven-dam, twelve-time-period dynamic programming model, and data for power generation and pollution abatement. The power generation data is derived using 1972 cost figures.     

EFFECTS OF SOIL TYPE,PLOT CONDITION,AND SLOPE ON RUNOFF AND INTERRILL EROSION OF TWO SOILS IN THE LAKE TAHOE BASIN1

ABSTRACT: Few studies have addressed sediment discharge due to interrill erosion from natural and minimally disturbed alpine and subalpine forested watersheds. Infiltration, runoff, and surface erosion of two Tahoe Basin soils under several conditions were investigated using rainfall simulation. A significant three-way interaction among soil type, plot condition, and slope was identified. Although high erodibiity was commonly associated with disturbance and/or high slope, this was not always the case. Soil type, plot condition, slope, and duration of the event were all found to be important factors in determining the amount of erosion. Decreased water clarity in Lake Tahoe has been partly attributed to increased algal growth associated with surface runoff and erosion from adjacent watersheds. Interpretive evaluation for resource management planning should be event based and carefully delineated on a sitespecific basis.     

ENERGY LOSS AND REPLACEMENT COST OF NAVIGATION OF THE SNAKE-COLUMBIA RIVERS1

ABSTRACT: A competitive relationship exists between power production and navigation in the allocation of water resources along the Snake-Columbia River Complex. This report identifies the energy losses within the power system and the replacement costs of water diversion which resulted from commercial and recreational navigation of the Complex over the period 1975–1977.     

LOW DISCHARGE PERIODS OF RIVERS IN THE UPPER VISTULA RIVER BASIN,POLAND1

ABSTRACT: A method is presented for determining low discharge periods of rivers based on threshold values defined in terms of MEAN OF MINIMUM SUMMER (WINTER) DISCHARGES. The method is used to determine summer low flow periods in the Vistula River basin in Poland. Analysis is based on daily discharge data for 84 basins of the Upper Vistula River which was collected by the Polish Institute of Meteorology and Water Economy.     

NATURAL VEGETATION AS A SOURCE OF DIFFUSE SALT WITHIN THE COLORADO RIVER BASIN1

Abstract: Foliage and litter leachate from selected natural vegetation in the Price River Basin (within the Upper Colorado River basin) was studied to determine the probable impact of plants on the amount of diffuse salt movement from rangeland watersheds. Calculations using concentrations of various leachates and characteristics of range sites expected to be high salt annual salt load to the Price River. It was therefore concluded that plants are not a significant source of diffuse salt within the Colorado River Basin.     

NITROGEN AND PHOSPHORUS IN SURFACE WATERS OF THE UPPER COLORADO RWER BASIN1

ABSTRACT: As part of a basinwide water-quality study, nitrogen and phosphorus data for the Upper Colorado River Basin from the Colorado-Utah State line to the Continental Divide were analyzed for spatial distributions, concentrations associated with various land uses, and temporal trends. Nitrogen and phosphorus concentrations generally increased in a downstream direction. Some nutrient concentrations were elevated at some sites in the upper parts of the basin in areas influenced by increasing urbanization. Sites were grouped according to land use and site type, and median nutrient concentrations were compared among groups. Sites within the agricultural areas of the basin generally had the highest concentrations of nitrogen and phosphorus; concentrations for main-stem, tributary, and urbanization sites were slightly lower than for the agricultural sites. Background sites, or sites with minimal land-use impacts, had very low median nutrient concentrations. Several sites with long-term data were analyzed for temporal trends in concentrations. Several statistically significant downward trends of low and moderate magnitude were observed for nitrogen and phosphorus species. No upward trends were observed in the data at any site.     

CONSUMPTIVE USE OF STREAMFLOW INCREASES IN THE COLORADO RIVER BASIN1

ABSTRACT: This study examined the disposition of streamflow increases that could be created by vegetation management on forest land along the upper reaches of the Colorado River. A network optimization model was used to simulate water flow, storage, consumptive use, and loss within the entire Colorado River Basin with and without the flow increases, according to various scenarios incorporating both current and future consumptive use levels as well as existing and potential institutional constraints. Results indicate that very little of the flow increases would be consumptively used at current use levels, or even at future use levels, if water allocation institutions remain unchanged. Given future use levels and economically based water allocation institutions, up to one-half of the flow increases could be consumptively used. The timing of streamflow increases, and the institutional constraints on water allocation, often limit the potential for consumptive use of flow increases.     

IMPLICATIONS OF A DRAWDOWN OF THE SNAKE-COLUMBIA RWER ON BARGE TRANSPORTATION1

ABSTRACT: The listing of the Snake-Columbia River salmon under the Endangered species Cut will lead to a set of river management changes aimed at species recovery. One measure almost certain to be implemented is a periodic river drawdown. A drawdown will speed fish migration downriver but will also temporarily close the river to barge transportation. Grain shippers in the region rely on the barge carriage to move a significant share of annual production to export elevators on the Lower Columbia. A number of other bulk commodities utilize barges as well. This study outlines the aggregate and distributional economic implications of a suspension of barge transportation resulting from a river drawdown.     

ENVIRONMENTAL IMPACT MITIGATION UNDER THE CLEAN WATER ACT AND THE NATIONAL ENVIRONMENTAL POLICY ACT: THE CASE OF TWO FORKS DAM1

ABSTRACT: The role of environmental mitigation in permitting decisions under Section 404 of the Clean Water Act and the National Environmental Policy Act is examined, addressing the extent to which compensatory mitigation is acceptable. The role of mitigation is examined both generically and specifically: first in the requirements of the Clean Water Act and NEPA, and then in the case study of the proposed Two Forks Dam. In both cases, the paper describes dual purposes of environmental protection legislation and mitigation: to protect the biophysical environment and maintain associated human values. Mitigation is found to be sometimes necessary and acceptable as compensation for unavoidable impacts of project development. However, the Two Forks case exemplifies that compensatory mitigation has also been employed as a mechanism to facilitate project development when practicable alternatives entailing less environmental impact are available. Acceptance of compensatory mitigation in such cases violates both the Guidelines of the Clean Water Act and the intent of that Act and NEPA to protect the biophysical environment and human welfare. A recent memorandum of agreement between the Corps and the EPA clarifies this policy, and suggests that permit applications which rely on compensatory mitigation when impacts are available may be denied.     

COMPARISON OF ANNUAL AND PARTIAL DURATION SERIES FLOODS ON THE MURRUMBIDGEE RIVER1

ABSTRACT: In current hydrologic practice flood frequency estimates are usually based upon either the annual or the partial duration series of floods. Recurrence intervals generated by each series are not equivalent, however, and conversion of recurrence intervals from one series to the other is usually achieved by reference to a mathematical function developed by Langbein in 1949. Data collected on the Murrumbidgee River in New South Wales suggest, however, that the Langbein conversion function does not always provide a reliable means of comparing recurrence intervals. For discharges more frequent than the three year annual flood the Langbein function understates the discrepancy between the two sets of recurrence interval by approximately 35 percent. Langbein's own North American data appear to be consistent with those collected on the Murrumbidgee River.     

THE TREE-RING RECORD OF SEVERE SUSTAINED DROUGHT1

ABSTRACT: Frequent and persistent droughts exacerbate the problems caused by the inherent scarcity of water in the semiarid to arid parts of the southwestern United States. The occurrence of drought is driven by climatic variability, which for years before about the beginning of the 20th century in the Southwest must be inferred from proxy records. As part of a multidisciplinary study of the potential hydrologic impact of severe sustained drought on the Colorado River, the physical basis and limitations of tree rings as indicators of severe sustained drought are reviewed, and tree-ring data are analyzed to delineate a “worst-case” drought scenario for the Upper Colorado River Basin (UCRB). Runs analysis of a 121-site tree-ring network, 1600–1962, identifies a four-year drought in the 1660s as the longest-duration large-scale drought in the Southwest in the recent tree-ring record. Longer tree-ring records suggest a much longer and more severe drought in 1579–1598. The regression estimate of the mean annual Colorado River flow for this period is 10.95 million acre-feet, or 81 percent of the long-term mean. The estimated flows for the 1500s should be used with caution in impact studies because sample size is small and some reconstructed values are extrapolations.     

COMPARISON OF FOUR ARTIFICIAL SUBSTRATES AND THE PONAR GRAB FOR BENTHIC INVERTEBRATE COLLECTION1

ABSTRACT: Four different bottom-placed artificial substrates were compared with the Ponar grab for collecting benthic invertebrates. Artificial substrate samples of organisms were larger and more diverse than those of the grab. Barbeque Basket samplers caught the most taxa and individuals and Beak Trays caught the least. Chironomids and crustaceans were dominant in artificial substrate samples. Exposure habitat (left or right bank) determined taxa availability, whereas sampler design determined suitability for colonization by the taxa. Diversity for Beak Tray samples was lower than that for other artificial substrates but higher than for Ponar samples. The Barbeque Basket, Bull Basket, and Multiple Plate samples were taxonomically similar. Ponar samples were different, and Beak Trays were of intermediate similarity. As qualitative samplers, Barbeque Baskets were 63 percent efficient, followed by Bull Baskets (55 percent), Multiple Plates (48 percent), Beak Trays (38 percent), and Ponar Grabs (6–10 percent). Bull Baskets required the least and Beak Trays the most replicates to be within a preselected percentage error of the mean at the 95 percent probability level for numbers of taxa and individuals, and for diversity. Under conditions of the study, Bull Baskets ranked highest, followed by Barbeque Baskets and Multiple Plates, in selected performance criteria. Differences between grab and artificial substrate samples are explainable in terms of major riverine habitats and characteristics of the collection methods.     

HYDROLOGICAL APPLICATIONS OF LANDSAT IMAGERY USED IN THE STUDY OF THE 1973 INDUS RIVER FLOOD,PAKISTAN1

ABSTRACT: During August and September 1973, the Indus River Valley of Pakistan experienced one of the largest floods on record, resulting in damages to homes, businesses, public works, and crops amounting to millions of rupees. Tremendous areas of lowlands were inundated along the Indus River and major tributaries. Landsat data made it possible to easily measure the extent of flooding, totaling about 20,000 km² within an area of about 400,000 km² south from the Punjab to the Arabian Sea. The Indus River data were used to continue experimentation in the development of rapid, accurate, and inexpensive optical techniques of flood mapping by satellite begun in 1973 for the Mississipi River floods. The research work on the Indus River not resulted in the development of more effective procedures for optical processing of flood data and synoptically depicting flooding, but also provided potentially valuable ancillary information concerning the hydrology of much of the Indus River Basin.