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Total Runoff (total + runoff)
Selected AbstractsAssessment of land-use impact on streamflow via a grid-based modelling approach including paddy fieldsHYDROLOGICAL PROCESSES, Issue 19 2005Seong Joon Kim Abstract To investigate the hydrologic impacts of land-use changes on streamflow for an urbanizing watershed with paddy fields, a grid-based daily hydrologic model was adopted. The model was calibrated with two years (2000,2001) of observed streamflow data and validated using 5 months (2001) of measured soil moisture data and 1 year (2002) of observed streamflow data. After the model was tested, it was run to estimate impacts of urbanization on each hydrologic component with the land-use data sets for 1986, 1994, and 2002 generated from Landsat TM satellite images. Total runoff increased from 41·4% (1986) to 44·9% (2002) for a 5·4% increase in urban area, implying that direct runoff increase exceeded baseflow decrease. Urbanization affected the proportions of direct runoff for each land-use category more than the change in total runoff and the ratio of direct runoff to total runoff. The change proportions in direct runoff for urban areas, paddy fields, and forest were 14·3%, ,9·8% and ,6·7% respectively for a 5·4% increase, 4·6% decrease and 3·4% decrease in each land-use area respectively. The results indicate that paddy fields play an important role in runoff regulation, and the evaluation method can assist regional policy makers in developing land management strategies that minimize hydrologic impacts on streamflow. Copyright © 2005 John Wiley & Sons, Ltd. [source] The simulation of heat and water exchange at the land,atmosphere interface for the boreal grassland by the land-surface model SWAPHYDROLOGICAL PROCESSES, Issue 10 2002Yeugeniy M. Gusev Abstract The major goal of this paper is to evaluate the ability of the physically based land surface model SWAP to reproduce heat and water exchange processes that occur in mid-latitude boreal grassland regions characterized by a clear seasonal course of hydrometeorological conditions, deep snow cover, seasonally frozen soil, as well as seasonally mobile and shallow water table depth. A unique set of hydrometeorological data measured over 18 years (1966,83) at the Usadievskiy catchment (grassland) situated in the central part of Valdai Hills (Russia) provides an opportunity to validate the model. To perform such validation in a proper way, SWAP is modified to take into account a shallow water table depth. The new model differs from its previous version mainly in the parameterization of water transfer in a soil column; besides that, it includes soil water,groundwater interaction. A brief description of the new version of SWAP and the results of its validation are presented. Simulations of snow density, snow depth, snow water equivalent, daily snow surface temperature, daily evaporation from snow cover, water yield of snow cover, water table depth, depth of soil freezing and thawing, soil water storage in two layers, daily surface and total runoff from the catchment, and monthly evaporation from the catchment are validated against observations on a long-term basis. The root-mean-square errors (RMSEs) of simulations of soil water storage in the layers of 0,50 cm and 0,100 cm are equal to 16 mm and 24 mm respectively; the relative RMSE of simulated annual total runoff is 16%; the RMSE of daily snow surface temperature is 2·9 °C (the temperature varies from 0 to ,46 °C); the RMSE of maximum snow water equivalent (whose value averaged over 18 years is equal to 147 mm) is 32 mm. Analysis of the results of validation shows that the new version of the model SWAP reproduces the heat and water exchange processes occurring in mid-latitude boreal grassland reasonably well. Copyright © 2002 John Wiley & Sons, Ltd. [source] Soil frost effects on soil water and runoff dynamics along a boreal transect: 2.HYDROLOGICAL PROCESSES, Issue 6 2001Simulations Abstract A physically based SVAT-model was tested with soil and snow physical measurements, as well as runoff data from an 8600 m2 catchment in northern Sweden in order to quantify the influence of soil frost on spring snowmelt runoff in a moderately sloped, boreal forest. The model was run as an array of connected profiles cascading to the brook. For three winter seasons (1995,98) it was able to predict the onset and total accumulation of the runoff with satisfactory accuracy. Surface runoff was identified as only a minor fraction of the total runoff occurring during short periods in connection with ice blocking of the water-conducting pores. Little surface runoff, though, does not mean that soil frost is unimportant for spring runoff. Simulations without frost routines systematically underestimated the total accumulated runoff. The possibility of major frost effects appearing in response to specific combinations of weather conditions were also tested. Different scenarios of critical initial conditions for the winter, e.g. high water saturation and delayed snow accumulation leading to an increased frost penetration, were tested. These showed that under special circumstances there is potential for increased spring runoff due to soil frost. Copyright © 2001 John Wiley & Sons, Ltd. [source] The role of seepage in erodibilityHYDROLOGICAL PROCESSES, Issue 1 2001L. O. Owoputi Abstract This paper describes a laboratory experimental study to examine the role of seepage in the soil-water erosion process. The study utilized a laboratory flume, which was subjected to both seepage and rainfall in order to determine the exact character of the influence of seepage on erosion rates. The results from the experimental tests performed on sand and sandy clay till are reported. The experimental results show that seepage, by itself, has little effect on erosion rates. However, the erosion caused by rainfall is increased when seepage is present. The increased erosion was not caused by an increase in the total runoff from the seepage. It was found that seepage has an effect on the erodibility of the sand and sandy clay till. The results also show that the impact of seepage on the erodibility of the sand is greater than that of the sandy clay till. Copyright © 2001 John Wiley & Sons, Ltd. [source] MANAGEMENT OF FLOOD CONTROL SUMPS AND POLLUTANT TRANSPORT,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 1 2001Edward H. Smith ABSTRACT: Levee sump systems are used by many riverine communities for temporary storage of urban wet weather flows. The hydrologic performance and transport of stormwater pollutants in sump systems, however, have not been systematically studied. The objective of this paper is to present a case study to demonstrate development and application of a procedure for assessing the hydraulic performance of flood control sumps in an urban watershed. Two sumps of highly variable physical and hydraulic characteristics were selected for analysis. A hydrologic modeling package was used to estimate the flow hydrograph for each outfall as part of the flow balance for the sump. To validate these results, a water balance was used to estimate the total runoff using sump operational data. The hydrologic model calculations provide a satisfactory estimate of the total runoff and its time-distribution to the sump. The model was then used to estimate pollutant loads to the sump and to the river. Although flow of stormwater through a sump system is regulated solely by flood-control requirements, these sumps may function as sedimentation basins that provide purification of stormwater. A sample calculation of removals of several conventional pollutants in the target sumps using a mass balance approach is presented. [source] | ||||||||||