Estimation of runoff in a watershed is a prerequisite for design of hydraulic structures, reservoir operation and for soil erosion control measures. Water resource planning and management is important and critical issue in arid and semi-arid regions. Runoff from a watershed affected by several geo-morphological parameters and for a particular watershed land use change can affect the runoff volume and runoff rate significantly. Several methods are investigated to estimate the surface runoff from a catchment but the Curve Number method is mostly used. Present study was undertaken to estimate surface runoff and water availability for two sites (Ozat-2 and Zanzesri) in the Ozat catchment situated in Junagadh, Gujarat, India using RS and GIS based curve number method. The Weight curve number for the ozat catchment is 73.00. The correlation coefficient between calculated and observed runoff was good for both catchments. In this study found that SCS-curve number method along with RS and GIS can be used successfully in semi-arid region to simulate rainfall runoff and to estimate total surface water.

Remote sensing based various land surface and bio-physical variables like Normalized Difference Vegetation Index (NDVI), Land Surface Temperature (LST), surface albedo, transmittance and surface emissivity are useful for the estimation of spatio-temporal variations in evapotranspiration (ET) using Surface Energy Balance Algorithm for Land (SEBAL) method. These variables were estimated under the present study for Ozat-II canal command in Junagadh district, Gujarat, India, using Landsat-7 and Landsat-8 images of summer season of years 2014 and 2015. The derived parameters were used in SEBAL to estimate the Actual Evapotranspiration (AET) of groundnut and sesame crops. The lower values NDVI observed during initial (March) and end (May) stages of crop growth indicated low vegetation cover during these periods. With full canopy coverage of the crops, higher value of NDVI (0.90) was observed during the mid-crop growth stage. The remote sensing-based LST was lower for agricultural areas and the area near banks of the canal and Ozat River, while higher surface temperatures were observed for rural settlements, road and areas with exposed dry soil. The maximum surface temperatures in the cropland were observed as 311.0 K during March 25, 2014 and 315.8 K during May 31, 2015. The AET of summer groundnut increased from 3.75 to 7.38 mm.day-1, and then decreased to 3.99 mm.day-1 towards the end stage of crop growth. The daily AET of summer sesame ranged from 1.06 to 7.72 mm.day-1 over different crop growth stages. The seasonal AET of groundnut and sesame worked out to 358.19 mm and 346.31 mm, respectively. The estimated AET would be helpful to schedule irrigation in the large canal command.

The present study was conducted in the Saurashtra region of Gujarat to demonstrate the development and validation of location and crop-specific composite drought index (CDI) using a linear combination of three parameters including meteorological drought index, vegetation drought index and inverse of maximum consecutive dry days%for major Kharif crops of the region i.e. cotton and groundnut. The performance of nine drought indices including six meteorological and three remote sensing-based vegetation indices wasevaluated in terms of correlation with district scale crop yields.The district-wise expressions of CDI were developed by assigning principal component analysis (PCA) based weights to parameters.Standardized Precipitation Evapotranspiration Index (SPEI)/ Reconnaissance Drought Index (RDI) among meteorological indices and NDVI Anomaly Index (NDVIA)/ Vegetation Condition Index (VCI) among vegetation indices were found suitable for generating district specific CDI expressions. The developed CDI showed higher correlation with Kharif cotton and Groundnut crop yields as compared to various meteorological as well as vegetation indices used in the study and effectively quantified major historic agricultural droughts.The average correlation coefficients of developed CDI with cotton and groundnut yields were 0.71 and 0.77 respectively. The correlations of CDI and crop yields for all CDI expression were highly significant with p<0.01. The method developed in the study will be useful to generate crop and region-specific multi-scalar drought indices by the amalgamation of multiple drought indices for assessing crop production losses.

In the era of decreasing irrigation water availabilities, the focus must be on decreasing crop production water footprints. The various irrigation water management like deficit irrigation, fertigation, and mulching along with MIS can help reduce water footprints. However, the effects of aerated drip irrigation on sweet corn performance under various options of irrigation water management are not yet examined elsewhere. So, it was assessed through field experiments for 2 years during the winter season of the year 2020-21 and 2021-22 at the research farm of the Junagadh Agricultural University campus at Junagadh having a soil texture of clay loam. Two air injection rates i.e. 0 and 12 % by volume of irrigation flow rate was imposed on 16 different treatment combinations of 2 irrigation levels (deficit irrigation-0.7 ETc and full irrigation-1.0 ETc {Crop Evapotranspiration}), 2 fertigation levels (deficit fertigation-0.7 RDF and full fertigation-1.0 RDF {Recommended Dose of Fertilizer}), 2 drip system type (surface drip and subsurface drip) and 2 mulch levels (mulch and no mulch). The aerated irrigation effects on the production of fresh cob yield were found different under various options of irrigation water management. Overall, on average, sweet corn cob yield increased by 8.94% due to aerated irrigation as compared to non-aerated and the results were found significant. The adoption of aerated subsurface drip irrigation under mulch with irrigation/fertigation scheduling at 1.0 ETc/1.0 RDF would result in higher yield if adopted by farmers, in other words, the yield increase of fresh cob would be almost twice as compared to traditional practices with benefit cost ratio (B/C) as 3.01 for aerated treatment and 2.78 for non-aerated treatment for subsurface drip irrigation under mulch with irrigation/fertigation scheduling at 1.0 ETc/1.0 RDF.

In the present study, the actual evapotranspiration was estimated using the remote sensing-based spatiotemporal approach of evaporative fraction for canal irrigation command (Ozat-II) in Junagadh, Gujarat state, India. The evaporative fraction (EF) in the spatial and temporal data is useful for the estimation of regional and temporal evapotranspiration (ET) for irrigation scheduling in irrigation command. The remote sensing-based surface energy balance algorithm for land (SEBAL) use the images from the satellite to estimates ET using EF. The land surface temperature (LST) and its relation with EF can be used to estimate ET using SEBAL approach. The Landsat-7, 8 images of summer season were used to derive the Normalized Difference Vegetation Index (NDVI) and LST, whose values ranged from 0.31 to 0.90 and 304.76 K to 311.00 K, respectively, in the agricultural land with crop in the command area. The SEBAL-based EF values were ranged from 0.11 to 1.00 over the canal irrigation command area. The temporal data of evaporative fraction indicate that the lower values of EF were observed during initial and end crop growth stages, i.e. March, first fortnight of April and late May which revealed the low vegetation cover. The values of EF increased in the agricultural crop land as the higher value of EF was observed as 0.84 during 116 (April 26, 2014) due to the application of irrigation from canal network and the lower value of EF was observed as 0.62 during 140 (May 20, 2014) during dry period of the season. As the NDVI increases, the evaporative fraction was also increased and the seasonal variation of NDVI was similar to the seasonal variation of EF. The relation between the EF and surface temperature, T S , was developed and gives the negative correlation with R 2 of 0.626 for agricultural land; this can be helpful to estimate spatiotemporal ET value. The remote sensing-based daily actual evapotranspiration (AET) values were ranged from 3.75 to 7.37 mm/day and FAO-56-based daily crop evapotranspiration (ET c ) values were ranged from 4.62 to 8.97 mm/d for groundnut crop. The water use efficiency (WUE, kg/ha.mm) for summer groundnut was estimated as 4.03 kg/ha.mm per the SEBAL-based actual evapotranspiration (AET) and as 4.38 kg/ha.mm as per FAO-56-based crop evapotranspiration (ET c ). The SEBAL-based AET can be used for the irrigation scheduling in the canal irrigation command for efficient water use.