Nurmohamed. R, Naipal. S, and F. DeSmed

Abstract: A grid-based distributed hydrological model WetSpa, compatible with ArcView Geographic Information Systems (GIS), was applied to the 7,860 km2 Upper Suriname River basin. Model parameters were derived from a digital elevation model (DEM), land use and soil type map of the basin. These parameters and the observed daily meteorological data (1978-1983) were used (1) to tests the performance of the WetSpa model to a large tropical basin, (2) to simulate water balance and outflow hydrographs, (3) to identify the different flow components and (4) to study the most sensitive model parameters for the study catchment. The statistical model evaluation results indicated that the model has a relatively high confidence and can give a fair representation of the flow hydrographs and the water balance for a complex terrain. The use of daily observations instead of hourly observations and the lack of other measurements of the hydrological processes (e.g. groundwater flow, infiltration) to calibrate/validate the model may have caused the large errors in low flows and high flows. The deviations between the observed and simulated flows may also be caused by the lack of a good representation of the meteorological conditions in the study area. The WetSpa modelalso provided insight into the main flow processes during the year. The most sensitive parameters for this basin were the interflow scaling factor ki, the groundwater flow recession coefficient Kg, the initial soil moisture K_ss and the correction factor for potential evapotranspiration K_ep.

Keywords: Geographic Information Systems, Hydrologic modeling, Hydrology, Upper Suriname river basin, WetSpa.

Santasmita Das and Dr. P.K. Paul

Abstract: The choice of site for small hydro in the inaccessible tracts of Himalayan region is a difficult task by the conventional methods. This leads to a considerable loss of time and money in selecting a proper site for small hydel. In this paper an attempt has been made to use GIS and Remote Sensing technology to arrive at various alternative sites available in the study area and finally to select the most technically suitable site. The Soil Conservation Service (SCS) Curve Number (CN) method has been utilized to identify the monthly average runoff of the site. The distributed curve number technique has been used in this work.

Keywords: Sub-watershed, Remote Sensing, GIS, Curve Number, Runoff.

Mapfumo E., Chanasyk D.S., and Chaikowsky C.L.A.,

Abstract: Studies of spatial variability and simulation of available soil water and extractable soil water are scarce and yet such data are essential in hydrologic and solute transport modeling. A study was conducted to characterize spatial variability of available soil water and extractable soil water on a reclaimed site in northern Alberta. The vegetation on site included grasses, legumes and shrubs. The site was reclaimed and the reconstructed profile was made up of 40-100 cm of clay loam/peat material overlying fine tailings sand. Soil water was measured using neutron moisture meters on a frequency of approximately two weeks during the growing season for a 2-year period. Spatial characterizations of available soil water (ASW) and extractable soil water (ESW) on the driest and wettest measurement days were conducted using geostatistical methods. A sample semi-variogram was estimated and several permissible theoretical models fitted and the model of best fit was determined using the Akaike Information Criterion (AIC). The spherical model was found to best represent the semi-variogram for available soil water and extractable soil water. Both the available soil water and extractable soil water had very high degrees of spatial dependence (> 99%) and the range of within which sample points were auto-correlated was less than 1 m. The conditional stochastic simulation of extractable soil water at unsampled locations that were 5 m north of the sampled locations indicated a high degree of uncertainty. This implies that generation of exhaustive data sets may require more sampling points at closer spacing to reduce uncertainty.

Key words: geostatistics, spatial variability, semi-variogram, uncertainty

Benedict M. Mutua and Andreas Klik
 

Abstract Soil erosion and sediment yield from catchments are key limitations to achieving sustainable land use and maintaining water quality in streams, lakes and other water bodies. Controlling sediment loading requires the knowledge of the soil erosion and sedimentation. However, sediment yield is usually not available as a direct measurement but estimated by using a sediment delivery ratio (SDR). An accurate prediction of SDR is important in controlling sediments for sustainable natural resources development and environmental protection. There is no precise procedure to estimate SDR, although the USDA has published a handbook in which the SDR is related to drainage area. This paper presents a new approach for estimating spatial sediment delivery ratio (SDR) for large rural catchments. The SDR is predicted using a Hillslope Sediment Distributed Delivery (HSDD) model in conjunction with a physically distributed hydrological model in a GIS environment. The new approach was developed and tested on Masinga catchment, a rural large catchment in Kenya. The hydrological model was validated using predicted and observed daily stream flows and a performance criterion based on Nash Sutcliffe coefficient of model efficiency was used. The developed model is not only conceptually easy and well suited to the local data needs but also requires less parameters, which offer less uncertainty in its application while meeting the intended purpose.

Keywords: soil erosion, sediment yield, sediment delivery ratio, modelling, Masinga catchment, GIS, hillslope

Vijay Kumar and Remadevi

Keywords: Geostatistics, Groundwater levels, Semivariogram, Kriging, India

Athanassios Bourletsikas, Evangelos Baltas and Maria Mimikou

Key words: Rainfall-runoff modeling, Forested watershed, Time-area method, Flow velocity, GIS, Greece.

M. Israil,  Mufid al-hadithi, D. C.  Singhal, Bhishm Kumar, M. Someshwar Rao and S. K. Verma

Abstract: Integrated geohydrological, isotopes and Geographical Information System (GIS) techniques have been used to delineate groundwater resources potential in the Piedmont zone of Himalayan foothill region, Uttaranchal, India. Thematic maps for hydrogeomorphology, slope, and drainage density have been prepared and integrated with the help of GIS by assigning the weights to various attributes controlling occurrence of groundwater to generate the groundwater potential map for the study area. The results indicates that the southern part of the study area has very good groundwater potential whereas the steeply sloping area in the northern part having high relief and high drainage density possesses poor groundwater potential. The groundwater potential zones are found in agreement with the available yield data of tubewell. Vertical component of recharge to groundwater due to precipitation varies from 3 to 13 %, which has been estimated using Tritium Tagging Technique. The estimated recharge to groundwater shows a linear relationship with environmental tritium contents in the water samples. This indicates that the precipitation is the major source of recharge in the study area. On the basis of environmental tritium contents, it has been found that recharge to groundwater is taking place at higher altitudes (300-400m, AMSL) in the Bhabhar region where the shallow and deeper aquifers have good interconnection. The estimated groundwater flow rate for the deeper aquifer is 1.2 m/d. The groundwater flow pattern estimated from isotope techniques has been validated from flow pattern determined by the depth of groundwater table.

Key words: piedmont, Himalayan foothill region, Tritium Tagging Technique, isotopic techniques.

Assefa M. Melesse, Vijay Nangia and Xixi Wang

Abstract: The spatial distribution of stocks of water is useful in studying flood, water pollution and water supply problems. Flood prone and closed basin watersheds benefit from spatial water balance studies in understanding the hydrologic processes and deal with excess water problems. In this study, we present results of a study of the hydrology Devils Lake basin of the Red River of the North, northeastern North Dakota partitioned in to two parts. Part 1 addresses the hydrometeorological analysis and lake surface area mapping of the basin and Part 2 deals with spatial surface water balance modeling using Landsat images and geographic information system (GIS). Hydrometeorological analysis using 100-years of historical record for the Devils Lake basin was conducted to capture the historical variability of the flood. In addition, surface area of the lake was mapped using Landsat image from 1991 to 2003. The Hydrometeorological analysis of the historical data showed the runoff inflow from upstream watersheds driven by snowmelt and spring rain falling on wet soil is the dominant source of the lake rise. Results show an increase in lake surface area by 117% between 1993 and 2003. The analysis also showed a correlation and possible interactions between the lake and the Spritwood aquifer indicating potential contribution of the groundwater flux to the water budget.

(Keywords: hydrometeorology, Devils Lake, remote sensing, GIS, runoff

Assefa M. Melesse, Vijay Nangia and Xixi Wang

Abstract: In this part of the study, grid-based spatial water balance approach was used to estimate the annual water balance of Devils Lake basin, hydrologically closed lake located in the Red River of the North basin, northeastern North Dakota. Landsat images from 1991 to 2003 were used in the study. Using spatial precipitation, land-cover and soils data, grid-based surface runoff was estimated based on the Curve Number method. The calibrated upstream runoff inflow for each grid cell was computed using a 10-m digital elevation model. Spatial evapotranspiration was estimated for the study area from remotely-sensed data using a surface energy flux model. The spatial water balance for each grid was constructed using grid geographic information system (GIS). The modeled average change in storage depth was compared to observed values of the lake stage. The grid GIS-based spatial surface water balance predicted the observed values with an average error of prediction of 0.12m. With better understanding of the groundwater contribution to the water balance, the prediction accuracy can be improved. The study ensures the applicability of the technique for surface water budget computation using GIS and remote sensing.

Keywords: water balance, Devils Lake, remote sensing, GIS, evapotranspiration, runoff, land use/land cover