B. C. Mal

Integrated remote sensing and GIS-based approach for assessing groundwater potential in West Medinipur district, West Bengal, India

A systematic planning of groundwater exploitation using modern techniques is essential for the proper utilization and management of this precious but shrinking natural resource. With the advent of powerful and high‐speed personal computers, efficient techniques for water management have evolved, of which RS (remote sensing), GIS (geographic information system) and GPS (Global Positioning System) are of great significance. In the present study, an attempt has been made to delineate and classify possible groundwater potential zones in the West Medinipur district of West Bengal, India using integrated remote sensing and GIS techniques. The thematic layers considered in this study are lithology, landform, drainage density, recharge, soil, land slope and surface water body, which were prepared using the IRS‐1D imagery and conventional data. All these themes and their individual features were then assigned weights according to their relative importance in groundwater occurrence and the corresponding normalized weights were obtained based on the Saatys analytical hierarchy process. The thematic layers were finally integrated using ArcInfo GIS software to yield a groundwater potential zone map of the study area. Thus, three different groundwater potential zones were identified, namely ‘good’, ‘moderate’ and ‘poor’. The area having good groundwater potential is about 1400 km2, which is about 15% of the total study area. The eastern portion and some small patches in the central and northern portions of the study area fall under moderate groundwater potential zone, which encompasses an area of 5400 km2 (55%). However, the groundwater potential in the western, south‐western and parts of north‐eastern portions of the study area is poor, encompassing an area of about 3000 km2. Moreover, the average annually exploitable groundwater reserve in the good zone was estimated to be 0.29 MCM/km2, whereas it is 0.25 MCM/km2 for the moderate zone and 0.13 MCM/km2 for the poor zone. Finally, it is concluded that the RS and GIS techniques are very efficient and useful for the identification of groundwater potential zones.

Optimal crop planning and conjunctive use of water resources in a coastal river basin

Due to increasing trend of intensive rice cultivation in a coastal river basin, crop planning and groundwater management areimperative for the sustainable agriculture. For effective management, two models have been developed viz. groundwater balance model and optimum cropping and groundwater management model to determine optimum cropping pattern and groundwater allocation from private and government tubewells according to different soil types (saline and non-saline), type of agriculture(rainfed and irrigated) and seasons (monsoon and winter). A groundwater balance model has been developed considering mass balance approach. The components of the groundwater balance considered are recharge from rainfall, irrigated rice and non-rice fields, base flow from rivers and seepage flow from surface drains. In the second phase, a linear programming optimization model is developed for optimal cropping and groundwater management for maximizing the economic returns. Themodels developed were applied to a portion of coastal river basin in Orissa State, India and optimal cropping pattern forvarious scenarios of river flow and groundwater availability wasobtained.

Sediment yield modelling of an agricultural watershed using MUSLE, remote sensing and GIS

A study was undertaken to estimate the sediment yield of the Karso watershed of Hazaribagh, Jharkhand State, India using modified universal soil loss equation (MUSLE), remote sensing (RS) and geographic information system (GIS) techniques. The runoff factor of MUSLE was computed using the measured values of runoff and peak rate of runoff at outlet of the watershed. The topographic factor (LS) was determined using GIS while crop management factor (C) was determined from land use/land cover data, obtained from RS and field survey. The conservation practice factor (P) was obtained from the literature. Sediment yield at the outlet of the study watershed was simulated for 345 rainfall events spread over a period of 1996–2001 and validated with the measured values. Nash–Sutcliffe simulation model efficiency of 0.8 and high value of coefficient of determination (0.83) indicated that MUSLE model estimated sediment yield satisfactorily.

Prediction of aeration performance of paddle wheel aerators

Abstract Aeration experiments were conducted in brick masonry rectangular tanks of dimensions 2.9×2.9×1.6 and 5.9×2.9×1.6 m to study the effect of geometric and dynamic variables on aeration process based on dimension analysis. Non-dimensional numbers relating to standard aeration efficiency (SAE), effective power (P) and theoretical power per unit volume (P/V) termed as SAE′, Ne and X, respectively, are proposed. An optimal geometric similarity of various linear dimensions was established. It has been established that neither the Reynolds criterion nor the Froude criterion is singularly valid to simulate either SAE′ or Ne, simultaneously for different sizes of aerators, even though they are geometrically similar. Occurrence of scale effects due to the Reynolds and the Froude laws of similitude on both SAE′ and Ne are also evaluated. Simulation equations uniquely correlating SAE′, Ne and X were developed which can predict the aeration performance of paddle wheel aerators having the optimised geometric dimensions as established.

Aeration characteristics of a rectangular stepped cascade system

Aeration experiments, maintaining nappe flow conditions, were carried out on a rectangular stepped cascade of total height 3.0 m to determine the total number of steps, slope of the entire cascade and hydraulic loading rate at which maximum overall aeration efficiency occurs, keeping the surface area of individual steps constant. Based on dimensional analysis, the overall aeration efficiency at standard conditions (E(20)) was expressed as a function of square of total number of steps (N(2)) and dimensionless discharge (d(c)/h), where d(c) and h represent critical depth in a rectangular prismatic channel and individual step height respectively. An empirical equation with E(20) as the response and N(2) and d(c)/h as the independent parameters was developed based on the experimental results subject to 36<or=N(2)<or =196 and 0.009<or=d(c)/h< or=0.144. The experimental results showed that the overall aeration efficiency (E(20)) for a particular step height of stepped cascade increases with increase in d(c)/h up to a certain value and then decreases. This may be due to at higher d(c)/h, i.e., at higher hydraulic loading rate, the flow approaches the transition zone and thereby aeration efficiency decreases. E(20) was also found to increase with number of steps at any hydraulic loading rate, because of the increased surface area of fall. The optimum number of steps, slope of the entire stepped cascade and hydraulic loading rate were found to be 14, 0.351 and 0.009 m(2)/s respectively producing the maximum value of overall aeration efficiency of 0.90.

Effect of spatial resolution on watershed characteristics and the ANSWERS model hydrological simulations for a small watershed

The present study was undertaken to investigate the effect of cell size variation on watershed characteristics and hydrological simulations of the physically based distributed parameter Areal Non point Source Watershed Environment Response Simulation (ANSWERS) model. The study is carried out in Banha watershed located in Upper Damodar catchment, Jharkhand, India having 16.13 km2 area (with average slope of 1.91%.) using Digital Elevation Model (DEM), GIS and remote sensing techniques for automatic extraction of the model input parameters. The spatial resolution (cell size) variation from 30m to 150m with incremental step of 30m influences the accuracy of watershed characteristics extracted from DEM. The flow path length and average watershed slope decreased by 53.71% and 20.94% respectively due to variation in cell size. Important watershed parameters such as drainage area, stream network, slope etc. were extracted most accurately automatically with variations less than 10% using DEM of 30m resolution through EASI/PACE and IDRISI GIS. Land use and land cover information generated from Indian Remote Sensing Satellite (IRS-1B, LISS-II) data at 30 m resolution resulted in overall classification accuracy greater than 88%. The watershed hydrological data from fifteen storms of 1995 and 1996 were used for the ANSWERS model cell size sensitivity study. The runoff, peak flow and sediment yield simulations by the model decrease as cell size increases from 30 m to 150 m. The model simulated peak flow at acceptable accuracy for 30 m cell size. The runoff and sediment yield simulations are not observed to be significantly different from the observed values up to 120 m cell size.

Performance of Hawaii-type automated fish feed dispenser

The traditional methods, such as broadcasting and the earthen-pot method, used to supply feed to the fish ponds are not very efficient. A simple, automatic fish feeder similar to that of the Hawaii-type was designed and fabricated, and its performance was studied in the laboratory. The feeder essentially consists of a rotating cycle wheel mounted on a slotted angle iron frame, feed boxes, trip arm, water tank and a float arrangement. The rotation of the wheel is created by winding cable around the nails fixed over the rotating wheel, passing it through a pulley and finally attaching it to a float at the lower end. The float rests on the water surface stored in a small tank. The float gradually descends along with the slow rate of fall of the water level in the tank due to discharge through an outlet attached at the bottom of the tank. As the float descends, the connecting cable rotates the wheel. The feed boxes move along with the rotation of the wheel, the trap-door strikes the trip arm and discharges the feed material into the pond. The unit can be set for desired number of applications of feed at desired time intervals.

Effect of Spatial Resolution on Watershed Characteristics and the AGNPS Model Hydrologic Simulations

The distributed parameter hydrologic and non point source (NPS) pollution models consider the spatial variability of watershed characteristics and simulate the distributed watershed processes by dividing the watershed into small elements called ‘cells’. Arbitrary selection of cell size for these models yields ambiguous results. Automatic extraction of watershed drainage characteristics from digital elevation model (DEM) is an effective alternative to the tedious manual mapping from topographic maps. Geographical information systems(GIS), DEM and remote sensing techniques provide faster, more efficient and accurate ways to extract parameters of distributed parameter models for each cell. In India, very limited applications of these advanced techniques have been made in NPS pollution modelling. The present aims to study the effect of cell size variation on hydrological simulations of the distributed parameter Agricultural Non Point Source (AGNPS) pollution model version 5.00 for a 16.13 km2 small watershed of the eastern India using DEM, GIS and remote sensing techniques for automatic extraction of the model input parameters.

Watershed Prioritization Using USLE, GIS and Remote Sensing

In the present study, prioritization of Karso watershed of Hazaribagh, Jharkhand State, India was carried out on the basis of average sediment yield data estimated from Universal Soil Loss Equation (USLE). In general, a major limitation in the use of hydrological models has been their inability to handle the large amounts of input data that describe the heterogeneity of the natural system. Remote sensing (RS) technology provides the vital spatial and temporal information on some of these parameters. A recent and emerging technology represented by Geographic Information System (GIS) was used as the tool to generate, manipulate and spatially organize disparate data for sediment yield modeling. Thus, the Arc Info GIS and RS (ERDAS Imagine 8.4) provided spatial input data to the model, while the USLE was used to predict the spatial distribution of the sediment yield on grid basis. The deviation of estimated sediment yield from the observed values in the range of 1.37 to 13.85 per cent indicates accurate estimation of sediment yield from the watershed. Subsequently, average sediment yields were estimated and the critical erosion prone areas of watersheds were arranged in the descending order of their sediment yields for prioritization purpose.