A SURVEY OF THE U.S. NATIONAL PRECIPITATION NETWORK1

ABSTRACT: Numbers and record lengths of precipitation stations were surveyed in the conterminous United States using climatological data published in 1975 by the National Weather Service (NWS). The total numbers of nonrecording (8247) and recording (3036) gages were about the same as in the 1940s and less than in the late 1950s; about 70 percent of the nonrecording gages have record lengths of 25 years or more. State network densities were increased exponentially with population density and long term precipitation average. Except for a few states, precipitation stations maintained by the NWS are adequate in numbers to ensure a 95 percent statistical probability that state sample means will estimate true means within ± 5 percent.     

PRECIPITATION DIFFERENCES AMONGST GCMs USED FOR THE U.S. NATIONAL ASSESSMENT1

ABSTRACT: Two general circulation models (GCMs) used in the U.S. national assessment of the potential consequences of climate variability and change (CGCM1 and HadCM2) show a large increase in precipitation in the future over the southwestern U.S., particularly during winter. This precipitation increase is an extension of a larger region of increased precipitation in the Pacific Ocean off the west coast of North America that is associated with a deepened and southward-shifted Aleutian Low, a weaker subtropical high, and warmer sea surface temperatures (SSTs). The models differ in their simulation of precipitation anomalies over the southeastern U.S., with CGCM1 showing drier conditions and HadCM2 showing wetter conditions in the future. While both models show decreased frequency of Atlantic storms, consistent with decreased meridional and land/sea temperature gradients, the more coastal position of the storm track in CGCM1 results in less precipitation than modern along the eastern seaboard of the U.S. During summer, differences in land surface models within the two GCMs sometimes lead to differences in soil moisture that feed back to the precipitation over land due to available moisture.     

SYNTHESIS OF DATA FROM STUDIES BY THE NATIONAL IRRIGATION WATER-QUALITY PROGRAM1

ABSTRACT: From 1986 to 1993, the National Irrigation Water-Quality Program (NIWQP) of the U.S. Department of the Interior studied whether contamination was induced by irrigation drainage in 26 areas of the Western United States. In 1992, a study to evaluate and synthesize data collected during these 26 investigations began. Selenium, boron, and molybdenum are the trace elements and DDT the pesticide most commonly found in surface water at concentrations exceeding chronic criteria for the protection of aquatic life. In six of the areas, the median selenium concentration exceeded the criterion. Aquatic-life criteria have not been developed for uranium, but the median uranium concentration exceeded the proposed Maximum Contaminant Level for drinking water in seven areas. A principal components analysis indicates that severity of selenium contamination is not related to the severity of contamination by boron, molybdenum, and arsenic. Arsenic, boron, molybdenum, and selenium concentrations are nearly the same in both filtered and unfiltered samples, which indicates that contaminant concentrations in filtered samples can be directly compared with biological-effects data developed using unfiltered samples. At a given site, selenium concentrations in surface water can change by an order of magnitude during the course of a year and from one year to another.     

A SURVEY OF STATE WATER CONSERVATION PROGRAMS IN THE U.S.1

ABSTRACT: Adequate water supplies are critical to the maintenance of a community's health and economic well-being. Across the nation communities are struggling to meet an expanding demand for water from municipal, industrial, agricultural, recreation, water quality, and power generation users. As the demand grows and communities actively compete with one another for a limited water supply, states are being called upon to help solve the problem. One possible solution that is being used in many areas is the development and implementation of a water conservation program to stretch the limited supply as far as possible. using a mailed survey, state water conservation programs and some of the characteristics of the different programs were documented. Responses to the nationwide survey were obtained from all 50 states. The specific water conservation program elements on which information was received from the survey included laws and restricted use, community assistance, education, research, and other services. Recommendations for states developing or considering the development of a water conservation program are outlined.     

BIOGEOCHEMICAL EFFECTS OF GLOBAL CHANGE ON U.S. NATIONAL PARKS1

ABSTRACT: Federal parks and other public lands have unique mandates and rules regulating their use and conservation. Because of variation in their response to local, regional, and global‐scale disturbance, development of mitigation strategies requires substantial research in the context of long‐term inventory and monitoring. In 1982, the National Park Service began long‐term, watershed‐level studies in a series of national parks. The objective was to provide a more comprehensive database against which the effects of global change and other issues could be quantified. A subset of five sites in North Carolina, Texas, Washington, Michigan, and Alaska, is examined here. During the last 50 years, temperatures have declined at the southern sites and increased at the northern sites with the greatest increase in Alaska. Only the most southern site has shown an increase in precipitation amount. The net effect of these trends, especially for the most northern and southern sites, would likely be an increase in the growing season and especially the time soil processes could continue without moisture or temperature limitations. During the last 18 years, there were few trends in atmospheric ion inputs. The most evident was the decline in SO₄² deposition. There were no significant relationships between ion input and stream water output. This finding suggests other factors as modification of precipitation or canopy throughfall by soil processes, hydrologic flow path, and snowmelt rates are major processes regulating stream water chemical outputs.     

SUMMARY OF MODIFICATIONS OF THE U.S. GEOLOGICAL SURVEY MODULAR,FINITE-DIFFERENCE,GROUND-WATER FLOW MODEL TO READ AND WRITE GEOGRAPHIC INFORMATION SYSTEM FILES1

ABSTRACT: The U.S. Geological Survey modular, three-dimensional, finite-difference, ground-water flow model, commonly called MODFLOW, has been modified so that it can read and write files used by a geographic information system (GIS). The modified model program is called MODFLOWARC. The design of MODFLOWARC parallels the design of the ground-water flow model program MODFLOW. The names of the variables, modules, and submodules used to explain the operations of MODFLOWARC were derived from the names used in MODFLOW. During the data input phase, MODFLOWARC reads array control records similar to the original control records of MODFLOW, except an additional variable is added. This additional variable is the name of the computer files containing array data in GIS format. Data output is achieved by setting record/input flags and by supplying a variable that is the name of the directory where the output data will be recorded. The modifications to MODFLOW were minimized so that MODFLOWARC will operate on an existing ground-water flow model without modifying array control records.     

PROPOSAL FOR A U.S. NATIONAL WATER ATLAS1

The U.S. National Committee for the International Hydrological Decade is proposing a National Water Atlas as a contribution to the improvement of the quality of information available for this Nation's large-scale planning and management studies. The atlas would provide hydrological maps of the United States and its principal basins and of its territories. The nationwide maps would be at a scale of 1:5,000,000 and the 17 principal basins at 1:2,500,000. The principal basins will be those delineated by the Water Resources Council. Wherever feasible and appropriate, the data will be presented with a common standard period of record, preferably 1941–70, as a base. Map subjects would include station networks, radiation, precipitation, snow and ice, evaporation, atmospheric vapor fluxes, surface-water discharge, ground-water storage and discharge, chemical quality, sediment discharge, water temperatures, and soil moisture. The list of maps subjects and types of data shown within each subject are flexible and open-ended so that additional maps could be added to the atlas as information is available or as new needs arise.     

NATIONAL WATER ASSESSMENT: NEEDED OR NOT?1

ABSTRACT A conceptual framework and the systematic collection of reliable information for application within the framework are the cornerstones of effective water planning. The ideal of strengthening these cornerstones was a driving force behind formation of the Water Resources Council and Council efforts, during its life, to develop the Principles and Standards and to complete two National Water Assessments. The Assessments contained voluminous data but never really became an integral component of the national water planning process. Before being disbanded in 1982, the Council solicited several appraisals of its assessment process. This paper reports one made by the university community in which experiences and opinions were obtained from 108 water research administrators and water policy experts.     

CLIMATIC CHANGE AND U.S. WATER RESOURCES: FROM MODELED WATERSHED IMPACTS TO NATIONAL ESTIMATES1

ABSTRACT: Water is potentially one of the most affected resources as climate changes. Though knowledge and understanding has steadily evolved about the nature and extent of many of the physical effects of possible climate change on water resources, much less is known about the economic responses and impacts that may emerge. Methods and results are presented that examine and quantify many of the important economic consequences of possible climate change on U.S. water resources. At the core of the assessment is the simulation of multiple climate change scenarios in economic models of four watersheds. These Water Allocation and Impact Models (Water‐AIM) simulate the effects of modeled runoff changes under various climate change scenarios on the spatial and temporal dimensions of water use, supply, and storage and on the magnitude and distribution of economic consequences. One of the key aspects and contributions of this approach is the capability of capturing economic response and adaptation behavior of water users to changes in water scarcity. By reflecting changes in the relative scarcity (and value) of water, users respond by changing their patterns of water use, intertemporal storage in reservoirs, and changes in the pricing of water. The estimates of economic welfare change that emerge from the Water‐AIM models are considered lower‐bound estimates owing to the conservative nature of the model formulation and key assumptions. The results from the Water‐AIM models form the basis for extrapolating impacts to the national level. Differences in the impacts across the regional models are carried through to the national assessment by matching the modeled basins with basins with similar geographical, climatic, and water use characteristics that have not been modeled and by using hydro‐logic data across all U.S. water resources regions. The results from the national analysis show that impacts are borne to a great extent by nonconsumptive users that depend on river flows, which rise and fall with precipitation, and by agricultural users, primarily in the western United States, that use a large share of available water in relatively low‐valued uses. Water used for municipal and industrial purposes is largely spared from reduced availability because of its relatively high marginal value. In some cases water quality concerns rise, and additional investments may be required to continue to meet established guidelines.     

APPLICATION OF THE U.S.G.S. DIFFUSION HYDRODYNAMIC MODEL FOR URBAN FLOODPLAIN ANAYSIS1

ABSTRACT: The two-dimensional Diffusion Hydrodynamic Model, DHM, is applied to the evaluation of floodplain depths resulting from an overflow of a leveed river. The environmental concerns of flood protection and high flow velocities can be better studied with the help of the two-dimensional DHM flow model than by use of the one-dimensional modeling techniques. In the test case, some of the predicted flood depth differences between the DHM and the one-dimensional approach (i.e., HEC-2) are found to be significant. Although the DHM generates considerable information, it is easy to use and does not require expertise beyond that required for use of the one-dimensional approaches.     

CORRELATION OF COPROSTANOL TO ORGANIC CONTAMINANTS IN COASTAL AND ESTUARINE SEDIMENTS OF THE U.S.1

ABSTRACT: Results from the National Status and Trends Program, a nationwide effort to evaluate U.S. coastal and estuarine environmental quality, are analyzed to provide information about regional sources of organic contaminants in the benthic environment. Spearman's rank correlation procedure is applied to measurements of coprostanol, a chemical tracer of sewage, and three classes of organic compounds in sediments. The results suggest that discharges from publicly owned treatment works are responsible for concentrations of the organic compounds encountered in the northeastern coastal region, while other sources may predominate in the other regions of the country.