COMPONENT TESTING WITHIN A COMPREHENSIVE WATERSHED MODEL1

ABSTRACT A comprehensive mathematical watershed model containing a complete soil moisture accounting system was used to simulate the hydrologic processes measured in one of the weighing lysimeters at Coshocton, Ohio. Data from a four-year rotation were used to calibrate the parameters initially selected for the model. Data from the succeeding four years were used to evaluate the predictions. Reasonable agreement was obtained between observed and predicted percolation and evapo-transpiration values.     

A CRITICAL APPROACH TO THE CALIBRATION OF A WATERSHED MODEL1

ABSTRACT: A complex watershed-scale water quality simulation model, the Hydrological Simulation Program-FORTRAN (HSPF) model, was calibrated for a 16 km² catchment. The simulation step size was 0.33 hours with predicted and recorded hydrologic flows compared on an annual and monthly basis during a total calibration period of four years. Unguided numerical optimization when applied alone did not yield a model parameter set with acceptable predictive capability; instead, it was necessary to apply a critical process that included sensitivity analysis, numerical optimization, and testing of derived model parameter sets to evaluate their performance for periods other than those for which they were determined. Using this critical calibration process, the model was proven to have significant predictive capability. Numerical optimization is an aid for model calibration, but it must not be used blindly.     

MODEL PREDICTIONS OF WATERSHED HYDROLOGIC COMPONENTS: COMPARISON AND VERIFICATIION1

ABSTRACT: Model predictions of the relatively simple soil compartment model SESOIL are compared with those of the more data-intensive terrestrial ecosystem hydrology model AGTEHM. Comparisons were performed using data from a deciduous forest stand watershed, a grassland watershed, and two agricultural field plots. Good agreement was obtained between model predictions for annual values of infiltration, evapotranspiration, surface runoff, and groundwater runoff. SESOIL model predictions also compare well with empirical measurements at the forest stand and the grassland watersheds.     

APPLICATION OF THE DR3M WATERSHED MODEL ON A SMALL URBAN BASIN1

ABSTRACT: Data collected at a 79-acre urban watershed in Albuquerque, New Mexico, were used to calibrate and verify the Distributed Routing Rainfall-Runoff Model, a parametric watershed model. Standard errors of estimate for the 38 calibration storms were 33 percent and 38 percent, respectively, for volumes and peaks; and for the 46 verification storms were 29 percent and 37 percent, respectively, for volumes and peaks. Correlation coefficients for peaks were 0.8 and 0.95, respectively, for calibration and verification storms.     

WATERSHED FUNCTIONS1

ABSTRACT: Watershed functions that dominate the hydrologic environment are identified and discussed. Hydrological and ecological functions are considered in relation to the storm and annual hydrographs, and to water quality. Two integrative watershed responses to these functions are also articulated. Since most of the Earth's water is in storage, consideration of the hydrologic cycle as movement between water storage sites enhances this functional and response characterization of the watershed which, in turn, suggests guidance and direction for the restoration of watershed functions.     

A COMPARISON OF METHODS OF ESTIMATING MEAN WATERSHED SLOPE1

ABSTRACT: Ten topographic analysis methods were employed to estimate watershed mean slopes for 13 small forested watersheds (32 to 131 mi²) in East Texas. Of the ten methods employed, the mean slope curve is the most accurate but also the most tedious and laborious one. The method can be simplified by measuring only the lengths of five contours and the areas between these contours within the watershed with little loss of its accuracy. Watershed slopes estimated by the contour length method, the grid contour method, the systematic slope sampling method, and the simplified contour length method are satisfactory for general purposes and relatively simple. The watershed circumference-stream length method, the length-width axis method, the Justin method, and the regression plane method are not suitable for estimating watershed slopes in East Texas without modification.     

USING A DISTRIBUTED ROUTING RAINFALL-RUNOFF MODEL1

ABSTRACT: Urban storm water data from four catchments near Miami, Florida, were collected and compiled by the U.S. Geological Survey and were used for testing the applicability of deterministic modeling for characterizing storm water flows from small land use areas. The four sites were:

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AN EXPANDING ROLE FOR SUBARCTIC WATERSHED RESEARCH1

ABSTRACT: It is increasingly recognized that natural resources research should in many cases be broadened in scope and oriented toward more general “environmental” problems. Locales with a history of “watershed” research can be eminently suited for development of comprehensive, environmental research programs. This is recognized in many research efforts of the International Biological Program (IBP), where watershed research sites have been successfully utilized for intensive investigations of process and function of selected ecosystems or ecosystem components. In the North American Subarctic there is almost no history of “watershed” studies. Basic data on hydrometeorologic parameters such as precipitation amounts and areal and seasonal distribution of runoff are scarce; the data framework within which environmental understanding can be structured is exceedingly sketchy. Opportunity exists in the discontinuous-permafrost settings of central Alaska to begin rectifying this situation. A basic program of multi-agency, multi-discipline research and data acquisition for the most significant hydrologic subregions is being developed, based around several existing environmental research areas (chiefly the Bonanza Creek Experimental Forest, the Caribou-Poker Creeks Research Watershed, the Wickersham Dome Fire Study Area, and a series of outlying sites).     

FORMAL EDUCATION IN WILDLAND HYDROLOGY AND WATERSHED MANAGEMENT IN NORTH AMERICA1

ABSTRACT: A survey was made to determine the status of formal education in wildland hydrology by colleges and universities in the United States, Canada, and Mexico. As of December 1977 nine institutions offered the B.S. degree, 18 the M.S. degree, and 17 the degree of Ph.D. with a major or minor in watershed management, forest hydrology, or range hydrology. In addition, 8 other schools offer a minor in watershed management. The survey indicated 44 schools in the United States offer a total of 157 courses, five schools in Canada offer 24 courses, and 1 in Mexico offers one course in the related areas. The survey illustrated rapid growth in education programs and it is anticipated that growth will continue.     

THE UNIT HYDROGRAPH: A SATISFACTORY MODEL OF WATERSHED RESPONSE?1

ABSTRACT: Some 96 flood events larger than the mean annual flood from 16 watersheds in the Commonwealth of Pennsylvania were used to derive unit hydrographs by the least-squares method. Analyses of the unit hydrographs were conducted to ascertain their response to watershed parameters, climatic and storm variables and locations within different hydrologic regions. Significant differences both within and among watersheds led to the formulation and testing of hypotheses stating that differences among watersheds are caused by physiographic differences while differences within watersheds result from climatic and storm differences. The analysis showed, that while many watersheds parameters strongly influence the shape of the unit hydrograph, only the storm variables duration and volume of precipitation excess produce significant differences. Seasonal differences were apparent but not proven statistically significant.     

WATERSHED RESPONSES TO CLIMATE CHANGE AT GLACIER NATIONAL PARK1

ABSTRACT: We have developed an approach which examines ecosystem function and the potential effects of climatic shifts. The Lake McDonald watershed of Glacier National Park was the focus for two linked research activities: acquisition of baseline data on hydrologic, chemical and aquatic organism attributes that characterize this pristine northern rocky mountain watershed, and further developing the Regional Hydro-Ecosystem Simulation System (RHESSys), a collection of integrated models which collectively provide spatially explicit, mechanistically-derived outputs of ecosystem processes, including hydrologic outflow, soil moisture, and snow-pack water equivalence. In this unique setting field validation of RHESSys, outputs demonstrated that reasonable estimates of SWE and streamflow are being produced. RHESSys was used to predict annual stream discharge and temperature. The predictions, in conjunction with the field data, indicated that aquatic resources of the park may be significantly affected. Utilizing RHESSys to predict potential climate scenarios and response of other key ecosystem components can provide scientific insights as well as proactive guidelines for national park management.     

HYDROLOGY OF A SMALL IMPOUNDMENT AND WATERSHED IN CENTRAL OKLAHOMA1

ABSTRACT: West Bitter Creek floodwater retarding structure site 3 in South Central Oklahoma was instrumented and records obtained and analyzed to obtain information concerning an impoundment water budget that is useful to landowners and designers of these impoundments. On-site loss of water from the impoundment was only 17 percent of the inflow during three years when the annual precipitation averaged 26 inches and the annual inflow averaged 1.4 inches. Runoff from an eroded area with no farm ponds was about 70 percent greater per unit area than from a portion of the watershed where 71 percent of the drainage area was controlled by farm ponds. A previous study indicated, however, that the ponds were reducing runoff only 13 percent. Loss of top soil increases runoff considerably. Only 24 percent of the total runoff into the impoundment was base flow. The flow rate into the impoundment was less than 0.05 cfs 70 percent of the time, and the inflow rate exceeded 10 cfs only 1 percent of the time. SCS runoff curve numbers varied between 57 and 96 for the impoundment watershed with an inverse relation between precipitation amount and curve number apprently caused by partial area runoff from impervious and semi-impervious areas. A comparison of measured event runoff versus event runoff computed by the SCS curve numbers gave an r² of only 0.44. However, the total computed surface runoff for eight years of record was less than 1 percent below the measured runoff which indicated the curve number method was a good tool for predicting long term runoff for the watershed.     

A WATERSHED APPROACH TO ECOSYSTEM MONITORING IN DENALI NATIONAL PARK AND PRESERVE,ALASKA1

ABSTRACT: The National Park Service and the National Biological Service initiated research in Denali National Park and Preserve, a 2.4 million-hectare park in southcentral Alaska, to develop ecological monitoring protocols for national parks in the Arctic/Subarctic biogeographic area. We are focusing pilot studies on design questions, on scaling issues and regionalization, ecosystem structure and function, indicator selection and evaluation, and monitoring technologies. Rock Creek, a headwater stream near Denali headquarters, is the ecological scale for initial testing of a watershed ecosystem approach. Our conceptual model embraces principles of the hydrological cycle, hypotheses of global climate change, and biological interactions of organisms occupying intermediate, but poorly studied, positions in Alaskan food webs. The field approach includes hydrological and depositional considerations and a suite of integrated measures linking key aquatic and terrestrial biota, environmental variables, or defined ecological processes, in order to establish ecological conditions and detect, track, and understand mechanisms of environmental change. Our sampling activities include corresponding measures of physical, chemical, and biological attributes in four Rock Creek habitats believed characteristic of the greater system diversity of Denali. This paper gives examples of data sets, program integration and scaling, and research needs.     

A CASE STUDY OF SHALLOW FLOW PATHS IN A STEEP ZERO-ORDER BASIN1

ABSTRACT: Soil water potentials, slope throughflow, runoff chemistry, and isotopic composition were monitored in a 97 m² zero-order basin within the Maimai 8 watershed on the South Island of New Zealand, for a natural rain storm and two artificial water applications. Contrary to results previously reported for other portions of the Maimai catchment, much of the runoff occurred as a shallow subsurface organic layer flow. For the 47 mm natural rain event, pre-storm soil matric potential ranged from ?60 to ?150 cm H₂O. No saturation was produced within the profile, and the majority of storm runoff emanated from flow within the organic horizon perched on the mineral soil surface. Hillslope applications corroborated this interpretation by showing >90 percent new water flushing with negligible mineral soil moisture response. Although the mechanisms cited in the text are not representative of the entire catchment, the study demonstrates: (1) the value of a combined physical-chemical-isotopic approach in quantifying slope processes, and (2) the heterogeneous nature and diversity of slope runoff pathways in a relatively homogeneous catchment.     

APPLICATION OF SCS INFILTRATION MODEL1

ABSTRACT: The SCS infiltration model was applied to the Ralston Creek watershed in eastern Iowa. The criteria to determine the various model parameters were revised to obtain a better agreement between the observed and computed total runoffs. A procedure to calibrate the infiltration model is presented. The infiltration model was used in conjunction with an overland flow model to develop flood hydrographs. The results indicate that SCS infiltration model adequately describe the distribution of losses.     

A QUASI-LINEAR SPATIALLY DISTRIBUTED CELL MODEL FOR THE SURFACE RUNOFF SYSTEM1

ABSTRACT: The paper presents a spatially distributed model consisting of cells that are interconnected in a pattern similar to the major drainage network of the watershed. Each cell receives as input the rainfall excess for the area represented by the cell as well as inflows from cells located upstream. Outflow from the cell is derived by routing the total input through the cell assuming it to be a linear reservoir during the storm. The time constant of the cells is however allowed to vary from storm to storm so that the model may be described as a quasi-linear model. The model was tested with rainfall excess and direct surface runoff data available for a medium size watershed with satisfactory results. The time constant was found to be related to the rainfall excess of the storms studied, its value decreasing with the increase in the total rainfall excess.     

UNDERSTANDING A WATERSHED FROM THE BIOLOGICAL VIEWPOINT1

In watershed management the effects of plants on water cannot be considered a constant and forgotten because: plants of different sizes and forms use water at different rates and plants of the same size differ in their needs for water because of anatomical differences. Many common denominators are present in all watersheds covered by vegetation. Forces exerted on the soil water by vegetation, climate and soil are the same kinds of forces. The differences between watersheds in water yield potential appear to be due to differences in the degree in which these forces are exerted. However, the influence of biotic factors are more individual. The similarities and differences existing between watersheds suggest some principles that can be used as guides to understanding individual watershed problems and as possible guides to determining when, how, and where to treat a given watershed. Eleven principles are given and their application to the definition and solution of biological or vegetational problems of watershed management are discussed.     

A DYNAMIC SYSTEM MODEL FOR SIMULATING SEDIMENT DISCHARGE1

ABSTRACT: A dynamic sediment discharge model was developed and proposed for the simulation of watershed systems. It war developed from an expansion of splash and flow erosion relationships under steady state conditions. It was described as a general erosion model that can be reduced to forms comparable to many conceptual soil erosion and sediment yield models. The model incorporates eight parameters such as rainfall intensities, runoff rates, and previous sediment discharges. The model was tested with two small watersheds with simulation results which were very satisfactory compared to the data.     

LONG-TERM CHANGES IN LOW-FLOW CHANNEL WIDTHS WITHIN THE SOUTH UMPQUA WATERSHED,OREGON1

ABSTRACT: Recent stream survey data (1989–1993) from 31 stream segments of 21 streams within the upper South Umpqua Watershed Oregon were compared to 1937 stream survey data collected from these same stream segments. Current low-flow wetted stream widths of 22 of the 31 surveyed stream segments were significantly different than in 1937; 19 stream segments were significantly wider while the remaining three stream segments were significantly narrower. In only 1 of 8 tributaries to the South Umpqua River which had headwaters within land designated wilderness area did low-flow stream channel width increase since 1937. Conversely, 13 of the 14 tributaries to the South Umpqua River which originated from lands designated as timber emphasis were significantly wider than in 1937. The observed change in stream width was linearly related to timber harvest (r²= 0.44), road density (r²= 0.45), and the amount of large organic debris remaining within the active stream channel (r²= 0.43). These findings suggest that timber harvest and road construction may have resulted in changes in channel characteristics. These channel changes may also be a factor in the observed decline of three of the four populations of anadromous salmonids within the basin.