WATER LOSS EQUATIONS AND COEFFICIENTS TO ESTIMATE RUNOFF FROM RAINFALL1

Infiltration models are based on physical characteristics of the soil and initial soil moisture. For a given soil it is based on the initial soil moisture distribution. A computer simulation model for flood runoff systems (FH-Model) was used to analyze 39 sets of rainfall-runoff data on four small watersheds ranging in size from 17 to 342 square kilometers located in the Yamaska River basin in Quebec. From these analyses, parameters and coefficients have been determined for a water loss (infiltration) equation. A method for determining the loss parameters, using a nonlinear least square curve fitting technique, is presented. Expressions were made to relate the loss parameters to antecedent precipitation. The equations were tested on 11 storm rainfall and runoff events on a watershed located in the same region and close agreements were found.     

ESTIMATING BASEFLOW VOLUME AND ITS UNCERTAINTY1

ABSTRACT: By using the exponential baseflow recession equation it is possible to estimate from a single discharge measurement the total volume of stream discharge during a baseflow period. If the discharge measurement is properly centered in the baseflow period the resulting estimate will be fairly precise, even if the baseflow recession coefficient is not known. Furthermore, based on an assumed probability distribution of the baseflow coefficient it is possible to estimate the uncertainty of the baseflow volume estimate. Estimates of baseflow volume and their uncertainty are potentially useful for estimating water budgets of lakes.     

Runoff and soil loss from steep slopes treated with low cost bioengineering measures

Soil loss and surface runoff patterns were studied in erosion plots developed on manmade steep slopes (60 percent) over three years (1997–2000) in which rainfall ranged from 1338.4 to 1429.2 mm/year. Surface runoff and soil loss was examined under three different rainfall intensity classes. Runoff was mainly controlled by the rainfall distribution pattern on the seasonal scale. The soil loss was influenced by runoff during the first year. Both soil loss and runoff were reduced due to bioengineering measures in the first year irrespective of species planted. In the third year, combined effects of growth of grasses on protected plots, soil compaction and sediment exhaustion was noticed on runoff and soil loss. This was reflected by reduction in the runoff and soil loss from untreated and treated plots. In the high intensity class, reduction in runoff in treated plots was about 50 percent in three years and reduction in soil loss ranged between 94–95 percent in all plots. Physical treatment with brushwood structures was more efficient in erosion control in the low intensity class.     

MANAGEMENT OF BASEFLOW AUGMENTATION: A REVIEW1

ABSTRACT: Baseflow augmentation refers to the temporary storage of subsurface water in floodplains, streambanks, and/or stream bottoms during the wet season, either by natural or artificial means, for later release during the dry season to increase the magnitude and permanence of low flows. Management strategies for baseflow augmentation fall into the following categories: (1) range management, (2) upland vegetation management, (3) riparian vegetation management, (4) upland runoff detention and retention, and (5) the use of instream structures. The benefits of a management strategy focused on baseflow augmentation are many, including: (1) increased summer flows, (2) healthier riparian areas, (3) increased channel and bank stability, (4) decreased erosion and sediment transport, (5) improved water quality, (6) enhanced fish and wildlife habitat, (7) lower stream temperatures, and (8) improved stream aesthetics. This review has shown that baseflow augmentation has been successfully accomplished in a few documented cases. Given its clear impact on soil and water conservation, particularly in the semiarid western U.S., it appears that baseflow augmentation is a concept whose time has come. Research is needed on how to successfully integrate baseflow augmentation within comprehensive resource management strategies.     

EFFECTS OF URBAN LAKES ON QUANTITY AND QUALITY OF BASEFLOW1

ABSTRACT: Man-made lakes have significant impacts on the hydrologic conditions in the watershed in which they are built. This paper examines the nature of the impact upon baseflow by comparing baseflow conditions at the outlet of the lakes with those elsewhere in the watershed. Situated in the upper reaches of a small watershed, the lakes studied have only a minor effect upon the magnitude of baseflow discharge, increasing it slightly from October to January, and decreasing it from May to September. Baseflow quality is substantially affected. Natural dissolved ions, as represented by magnesium, are generally decreased in concentration and total load by the lakes. Road salt related inons are substantially increased in both concentration and total load in the baseflow. Surface runoff stored in the lakes is extremely enriched in salt in the winter, and the storage capacity of the lakes is sufficient to maintain winter salt concentrations in the baseflow near the lakes until summer. The storage effect also tends to damp out seasonal fluctuations in baseflow chloride content which are extreme in suburban watersheds. The difference in quality between the lake and non-lake baseflows and the linear distance needed for complete mixing are used as measures of the magnitude and distal extent of the lake effect on baseflow quality.     

SENSITIVITY OF HIGH-ELEVATION STREAMS IN THE SOUTHERN BLUE RIDGE PROVINCE TO ACIDIC DEPOSITION1

ABSTRACT: The Southern Blue Ridge Province, which encompasses parts of northern Georgia, eastern Tennessee, and western North Carolina, has been predicted to be sensitive to impacts from acidic deposition, owing to the chemical composition of the bedrock geology and soils. This study confirms the predicted potential sensitivity, quantifies the level of total alkalinity and describes the chemical characteristics of 30 headwater streams of this area. Water chemistry was measured five times between April 1983 and June 1984 at first and third order reaches of each stream during baseflow conditions. Sensitivity based on total alkalinity and the Calcite Saturation Index indicates that the headwater streams of the Province are vulnerable to acidification. Total alkalinity and p11 were generally higher in third order reaches (mean, 72 μeq/θ and 6.7) than in first order reaches (64 μeq/θ and 6.4). Ionic concentrations were low, averaging 310 and 340 μeq/θ in first and third order reaches, respectively. A single sampling appears adequate for evaluating sensitivity based on total alkalinity, but large temporal variability requires multiple sampling for the detection of changes in pH and alkalinity over time. Monitoring of stream water should continue in order to detect any subtle effects of acidic deposition on these unique resource systems.     

CLASSIFICATION OF ENVIRONMENTAL HYDROLOGIC BEHAVIORS IN THE NORTHEASTERN UNITED STATES1

ABSTRACT: Environmental response to acidic deposition results from movement of water through the ecosystem. As a part of the environmental studies for acidic deposition sponsored by the U.S. Environmental Protection Agency (EPA), hydrologic classification based on regional baseflow properties was done. To obtain the amount of baseflow, a flow separation method was developed based on the division of streamflows into “baseflow” and “other” runoff sources. Because of the differences in the flow paths and exposure duration, the two components were assumed to be associated with distinct geo-chemical responses. Individual annual hydrographs were analyzed using 31 separation slopes to determine the amount of baseflow. A total of 1575 streamflow stations in the Northeastern U.S. were analyzed through the access of a long-term daily stream-flow data base. An interactive computer program was developed to obtain baseflow properties and other hydrologic characteristics of each station. The output from this analysis was used to perform cluster analysis to classify streamflow behaviors. The clustering output showed different regional boundaries than those currently used by the EPA for water quality studies.     

IMPACT OF SURFACE COAL MINING ON THREE OHIO WATERSHEDS – GROUND-WATER CHEMISTRY1

ABSTRACT: A study was conducted to determine the effects of surface mining and reclamation on ground-water chemistry in three saturated zones in each of three small East-Central Ohio water-sheds. The extensive disturbances of mining and reclamation: (1) caused more changes in constituent concentrations in the upper zone than in lower zones, most of which were statistically significant increases (many were “drastic”); (2) affected ground-water chemistry in lower zones - those that were not physically disturbed; (3) tended to increase the frequency of exceedance of regulated constituents in all saturated zones; and (4) affected the chemistry of surface baseflow water at the watershed outlets. Several constituents were still changing at the end of the project within all sites and zones.     

Modeling the Effects of Land Use Change on the Water Temperature in Unregulated Urban Streams

Streams, in their natural state, are typically diverse and biologically productive environments. Streams subject to urbanization often experience degradation brought about by the cumulative effects of flow alteration, unsanitary discharge and channelization. One of the water quality parameters affected by urbanization is stream temperature. This study offers a model for predicting the impact of land use change on the temperature of non-regulated streams during extreme events. A stream temperature model was created by considering the gains and losses of thermal energy resulting from radiation, convection, conduction, evaporation and advection. A sensitivity analysis showed that out of 14 variables, shade/transmissivity of riparian vegetation, groundwater discharge, and stream width had the greatest influence on stream temperature. These same three variables are highly influenced by land use. Individual component models were developed to predict how urbanization changes stream width and baseflow discharge. Using 3-D computer modeling, a model was also developed to illustrate the effects of altering the extent and composition of riparian vegetation on streams with different orientations. By modeling these three variables as a function of urbanization, the results became inputs into the stream temperature model. The critical urban stream temperature model (CrUSTe), an aggregation of these four models, allows the prediction of stream temperature change as a result of amount, type and location of urbanization within a watershed. It has the potential to become a valuable tool for environmental managers.     

EVALUATION OF INFLOW TO MIRROR LAKE,NEW HAMPSHIRE1

ABSTRACT: Measured stream discharge plus calculated ground water discharge (total measured runoff) were compared with runoff calculated by the unit-runoff method for the two largest watersheds of Mirror Lake for 1981–1983. Runoff calculated by the unit-runoff method, using Hubbard Brook watershed 3 as the index watershed, was greater than the total measured runoff into Mirror Lake during periods of high flow and slightly less than the total measured runoff into Mirror Lake during periods of low flow. Annual calculated unit runoff was 17 to 37 percent greater than total measured runoff. Differences in monthly runoff are far greater, ranging from 0 to greater than 100 percent. For high flows the calculated unit runoff is about 2 times greater than total measured runoff. For low flows the northwest basin of Mirror Lake has the greatest ground water contribution compared to the other two basins. In contrast, Hubbard Brook watershed 3 has the least ground water contribution.     

REGIONALIZATION OF STORM HYETOGRAPHS1

ABSTRACT: Regionalization of design storms can enhance their utility. Otherwise they have to be separately developed for different regions. Huff curves developed from point rainfall data collected at Coshocton, Ohio, and Chicago, Illinois, and from area-averaged Illinois and Texas precipitation data, are compared. The curves are similar in shape and position, with some visual differences depending on quartile. Kolmogorov-Smirnov tests showed no significant differences in moat of the comparisons. Where significant differences existed, they may not represent real differences due to the small number of storms sampled. Consequently, regionalization of Huff curves from Ohio to Illinois to Texas may be appropriate. The comparison of Huff curves is affected to an unknown degree both by the effects of area averaging of data and by basis. of-development differences. The effects of observed differences in Huff curves on watershed response variables (e.g., peak flow) requires further study.