Automatic extraction of tank outlets in a sub-watershed using digital elevation models

Watersheds contain many sub-watersheds (SWS) and the existence of a number of "small reservoirs" also called "tanks", located near the outlet points of the SWS, that serve as water-harvesting and storage structures, is common today. Estimation of the volume of water collected in these tanks, and determining the spatial and temporal distribution of the available water at various locations in the watershed are the two main aspects in agricultural land-use management. While, geographic information systems (GIS)-based approaches are used in estimating the volumes of water, routing is carried out in passing these volumes through the channels to the outlet of the main watershed. Extraction or determination of the location of the outlets of these tanks therefore. becomes essential to know the points where the water is available and where from it could be distributed appropriately. An algorithm was developed for automatic identification or location of tank outlets as well as tank boundaries, wherein the advantages of digital elevation models (DEM), that have become an essential and integral part of distributed, i.e. GIS-based approaches in hydrological modelling, are used beneficially and to overcome the difficulty in locating these tank outlets manually. The details of the algorithm are reported in this paper. A program in 'C' has been developed and the algorithm is tested in the study area of Kalyanakere SWS, Karnataka, India and the results of the algorithm match excellently with the field data. (C) 2002

Fuzzy class membership approach to soil erosion modelling

To optimize the use of the available land and water resources of a watershed for sustainable agricultural production, soil erosion assessment and conservation are essential. The Universal Soil Loss Equation (USLE) is a widely accepted model (Wishmeier and Smith, 1965. Predicting Rainfall Erosion Losses from Cropland (Agricultural Handbook No. 282). USDA. Washington, D.C.) for assessing soil erosion and to account for the most important factors. Conventional approaches to classification are designed to assign a given area element (pixel) to a single erosion class. However, the soil and other physical parameters might vary spatially within a pixel and it may not correspond entirely to a single erosion class. To determine the loss of information on the susceptibility to erosion a fuzzy class membership approach was used to assign partial grades to the erosion classes. In the present studies, a spatially distributed approach was used to consider the influence of the spatial variation in the soil and other physical parameters in soil erosion assessment in the study area, Kalyanakere subwatershed Karnataka, India, using the USLE model. The emphasis of the studies was laid on the use of a fuzzy class membership approach in soil erosion classification, and to develop a criteria table specifying the erosion parameter values related to erosion susceptibility classes from available literature to apply fuzzy class membership approach for the classification. Salient features of the approach and the results of the study are presented in this paper. (.

Kinetics of thermal decomposition of strontium zirconyl carbonate, Sr2Zr2O5CO3

The kinetics of decomposition of the carbonate Sr2Zr2O5CO3, are greatly influenced by the thermal effects during its formation. (α−t) curves are found to be sigmoidal and they could be analysed based on power law equations followed by first-order decay. The presence of carbon in the vacuum-prepared sample of carbonate has a strong deactivating effect. The carbonate is fairly crystalline and its decomposition leads to the formation of crystalline strontium zirconate

Luminescence of Eu2+Eu^{2+} in strontium aluminates prepared by the hydrothermal method

Preparation of Sr-aluminates in fine powder form, with Al/Sr ratio varying from 2 to 12 has been attempted by the hydrothermal method, starting from $Al_2O_3.xH_2O$ gel containing europium and $Sr(OH)_2$ at 240 – $250^0C$. The products are annealed at 850 – 1150°C in $N_2 + H_2$ atmosphere to yield, efficient blue to green luminescent phosphors. The predominant phase isolated belongs to the family of ‘stuffed’ tridymite-nepheline structures, having the general formula, $Sr_n Al_2O_{3+n}$ where n $\leq$ 1. With decreasing n-value, the relative intensity of the 405 nm emission band increases in preference to that of the 510 nm emission. The excitation spectra as well as the EPR results indicate the presence of $Eu^{2+}$ in the vacancy-associated nonequivalent sites. In presence of $H_3BO_3$ in the hydrothermal medium, aluminoborates such as $SrAl_5BO_{10}, Sr_2Al_2B_2O_8$ and $Sr_3Al_6B_8O_{24}$ are produced, whose only emission maximum around 400 nm remains as a band even at $LN_2$ temperature