K. D. Sharma

Rainwater infiltration into a bare loamy sand

ABSTRACT In order to design micro-catchment water harvesting systems in the Indian desert, rainwater infiltration experiments were conducted on a representative loamy sand soil for a period of six years. Plots with three slopes—0.5, 5 and 10%, and five slope lengths—5.12, 7.0, 8.5, 10.75 and 14.5 m were used. With dry antecedent soil conditions, infiltration is governed by rainfall depth, whereas with wet antecedent soil conditions, raindrop impact (intensity) which forms a crust over the soil surface, is the deciding factor. Infiltration decreases significantly with increasing slope due to reduction in the time available for rainfall to infiltrate, but slope length has no significant effect. A graphical multiple curvilinear model to predict rainfall infiltration using rainfall and basin characteristics is developed and the goodness of fit is tested.

A practical approach to rainfall-runoff modelling in arid zone drainage basins

Abstract A package of simulation models has been developed to study the hydrological processes controlling runoff and to predict flow hydrographs in the Indian arid zone. The models describe rainfall-runoff in the upland phase and the interaction between runoff and transmission losses in the channel phase, so as to derive the drainage basin outflow hydrograph. In the upland phase the rising limb of the hydrograph is predicted through a regression model and the recession through a conceptual analogue of discharge from a single leaky reservoir. The leaky reservoir is described by a continuity equation and by discharge-stage and storage-stage relationships at the outlet. In the channel phase the governing equations for movement of a flood wave subjected to the transmission losses are simplified through a time averaging process to develop an ordinary differential equation describing transmission losses as a function of distance, inflow, channel width, time parameters of flow and effective hydraulic conductivi...

Runoff estimation using Landsat Thematic Mapper data and the SCS model

Abstract Landform, drainage pattern, slope, soil, vegetation and land use/land cover, all of which control surface runoff and peak flow, can be evaluated and mapped reliably and reasonably through Landsat Thematic Mapper (TM) false colour composites of the post-monsoon season. Runoff curve numbers (CN) determined from those data predicted the runoff depth and peak flow with a coefficient of determination of 0.970 and 0.863 respectively; thereby indicating that, in terms of accuracy, speed and cost, the Landsat TM data are of great significance for estimating surface runoff via the SCS model in the arid environment of northwest India.

Satellite remote sensing for detecting the temporal changes in the grazing lands

Traditional grazing lands in the Indian arid zone can be identified and mapped, reliably and reasonably within ±10% accuracy, through Landsat TM false colour composite of bands 2,3,4. Comparative study of Landsat TM and the Survey of India topographical maps revealed reduction in the areal extent of the grazing lands in the Jodhpur district up to 9 to 30% over a period of 28 years, between 1958 and 1986, due to the human activity like cultivation and urbanisation resulting in the desertification of the adjoining agriculturallands.

Runoff behaviour of water harvesting microcatchments

Abstract The relationship between rainfall and runoff has been observed over a period of 7 years on sandy loam soils of the Indian Arid Zone. Fifteen microcatchment areas (MC) were studied; these were formed by combinations of three slopes (0.5, 5 and 10%) and five lengths (5.12, 7.0, 8.5, 10.75 and 14.5 m) with corresponding areas of 252, 324, 360, 396 and 432 m2. These MCs can produce 13.3–45.4% runoff depending upon their morphological characteristics. Over the 7-year period, threshold rainfall reduced by half and runoff efficiency doubled due to the formation of a less pervious soil crust over the MC surface; it became denser each year.

Effect of runoff concentration on growth and yield of jujube

Abstract Different combinations of slope (0.5, 5 and 10%), slope length (5.12, 7.0, 8.5, 10.75 and 14.5 m) and catchment size (0, 31.5, 54, 72, 99 and 144 m 2 ) aimed at generating runoff supplement of 200–400 mm per tree were studied with respect to yield of runoff, soil moisture storage and fruit yield of jujube ( Zizyphus mauritiana Lam.) under hot arid conditions. The runoff and soil moisture storage increased with the slope and decreased with the slope length. Similar trends were observed with regard to the fruit yield. Catchment/planted area ratios of 2:1, 1.5:1 and 0.87:1, respectively, are recommended for higher yields of jujube on slopes of 0.5, 5 and 10% with slope lengths of 8.5, 7.0 and 5.12 m.

DISTRIBUTED NUMERICAL RAINFALL–RUNOFF MODELLING IN AN ARID REGION USING THEMATIC MAPPER DATA AND A GEOGRAPHICAL INFORMATION SYSTEM

A transient one-dimensional finite-difference model describing the partitioning of precipitation between surface run-off, soil moisture storage and deep percolation, through the coupling of saturated and unsaturated zones, has been implemented in a geographical information system including data on vegetation cover derived from the Landsat Thematic Mapper. The model was used to simulate both the rainfall excess and the resultant outflow hydrographs for a small arid zone drainage basin in the Andean regions of Argentina. The overall hydrograph shape, peak discharge, run-off volume and flow duration are predicted within a relative squared error of 13.2%.

Satellite remote sensing for soil erosion modelling using the ANSWERS model

Abstract The distributed parameter model ANSWERS was used to predict runoff and soil loss from three agricultural watersheds in the arid zone of India. Model input parameters such as landform, drainage, soil and land use/land cover were derived from Landsat Thematic Mapper false colour composites and limited ground truth. The model predicted hydrographs and sediment graphs within acceptable limits. ANSWERS underpredicted the total soil loss by factors of 2.6 to 3.6. Reasons for these results are discussed.

Role of satellite remote sensing for monitoring of surface water resources in an arid environment

Water bodies up to 0.9 ha surface area, which are indistinguishable by Landsat Multispectral Scanner (MSS) due to the latters poor spatial resolution of 80 m, can be identified and mapped reliably and reasonably within ±10% accuracy by Landsat Thematic Mapper (TM) false colour composite because of its higher spectral and spatial resolution of 30 m. Comparative study of Landsat TM and the Survey of India topographical maps revealed reductions in the water surface and drainage basin areas up to 1.8 to 2.4 and 6.0 to 8.0 times, respectively, over a period of 28 years (1958–1986) due to the biotic interference resulting in desertification in the large adjoining areas.

Modelling suspended sediment flow in arid upland basins

Abstract A conceptual basin model of the instantaneous unit sediment graph was developed for sediment graph prediction from arid upland basins by routing mobilized sediments through a series of linear reservoirs. The sediment graphs generated by convolution of the instantaneous unit sediment graph compared reasonably well with the observed ones for four representative arid upland sub-basins in the Luni basin, India. The mobilized sediment during a storm was related to effective precipitation and the parameters of the model were estimated from observed events. The model can be applied to ungauged flow events through parameterization.