Snow melt runoff simulation and seasonal snowmelt volume forecast using Remote Sensing and Geographic Information System Model The Martinec - Rango model has been successfully used in the United States, Japan, Poland and French Alps. In addition to snow cover data, the model requires temperature and precipitation as inputs. These input parameters are necessary in each of the elevation zones. Precipitation and temperature are generally measured in the lower altitudes of the Himalayan basins. These parameters are not representing the higher altitudes of the basin. The degree - day factor is obtained from an empirical formula as a = 1. 1 pslpw where ps is density of snow and pw is density of water. The large variation of degree - day factor is experienced in Beas basin above Manali due to large difference in elevations as well as it is not possible to calculate in each of the elevation zone. The model accepts satellite based snow cover inputs in each of the elevation zones. The snow cover area estimation in each of the elevation ranges- could not be carried out accurately due to large difference in elevations. In view of the above fact, the model has been modified wherever necessary, to suite the. Himalayan watershed The snowmelt on any day may be expressed as the ordinate of normal recession curve together with additional discharge due to snowmelt and rain in the catchment on that day, thus the discharge on the n+lth day is given by  where Q - average daily discharge in m3 sec-1 SM - Snowmelt volume, M 3 RI - Rain input volume, M3 K - recession coefficient a - degree - day factor, mm. oC . d-1 Tsub>max - maximum atmospheric temperature, oC A - snowcover area, in sq.km p - precipitation at base station at Manali in mm g - orographic increase in precipitation x - percentage of snowfall i - elevation zone n - sequence of days during the discharge computation period. Methodology Snowmelt runoff model based on Rango & Martinec (1979) with appropriate modification has been developed in "C". These routines are invoked in ARC/INFO - GIS environment through systematic sequences (Through AML) as customised application interface called SRM-GIS. Image processing software package EASI/PACE functions available in developers toolkit are used to determinate snow line altitude and to, calculate snow cover area, percent snow cover area using area - elevation data. The package is a semi-automated with graphical functions available in IBM, RISC 6000 workstation. Structure of SRM-GIS The hydrometeorological data of measured discharge, temperature (minimum and maximum), precipitation data ( rain and snow ), digital elevation data of the watershed and the satellite data form inputs for SRM-GIS package and hydro-meteorological data are kept as .dat filesand satellite & DEM are kept as .pix files. The package is designed and developed with a set of pull-down menus. The main menu in this package consists  Image Processing Module Snowcover area Estimation invokes EASI/PACE image processing environment, open display window and loads satellite data (FCC). The user has to enter the date of pass (Date of acquire) file name of image. By clicking, along the snow line it automatically calculates the average snow line altitude and calculate snow cover area, percent snow cover area by area-elevation method.
The database module invokes data menu which contain the input data used for simulation purpose which can be displayed and viewed. Model Calibration module This module calculates recession coefficient, degree-day factors and snow/rain coefficients. It calculates recession coefficients for given period starting form the given year. If given period is more than the years in data file it calculate till the end of data base year. It calculate degree-day factors for the year of simulation. It calculate Snow/Rain coefficients for observed temperature and percent snowfall. All these coefficients displayed on monitor in a window. licking on model calibration invokes model menu which calculates different coefficients.
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