The reliability of estimates of reference evapotranspiration (ET0) using pan evaporation (Epan) depends on the accurate determination of pan coefficients (Kpan). Six ET0 models were evaluated for their usefulness using 33-year climatological dataset of a semi-arid region of the Gujarat state of India. The equations compared include Cuenca (1989), Allen and Pruitt (1991), Snyder (1992), Modified Snyder (Grismer et al., 2002), Orang (1998), and Pereira et al. (1995). The ET0 data, calculated using daily Kpan values from these equations, were compared to the Food and Agricultural Organization (FAO)-Penman-Monteith (FAO56-PM) method as a reference. Based on the visual comparison as well as from the statistical criteria, ET0 values computed using Modified Snyder and Orang model have very close agreement with the FAO56-PM method for daily, monthly, and annual estimates as compared to other approaches. The sequential performances of the explored models was found as: Modified Snyder (Eqn. 5) > Orang (Eqn. 6) > Cuenca Eqn. (2) > Allen & Pruitt (Eqn. 3) > Snyder (Eqn. 4) > Pereira et al. (Eqn. 7) model. Therefore, the Modified Snyder model (Grismer et al., 2002) could be recommended as the best model for ET0 computations under these prevailing climatic conditions for a semi arid region.

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Aims: The research work was carried out to find suitable sites for rainwater harvesting in Dhatarwadi river basin of Amreli district of Gujarat, India using remote sensing and geographic information system along with analytic hierarchy process. Place and Duration of Study: This study was carried out at College of Agricultural Engineering and Technology, Junagadh Agricultural University, Junagadh, Gujarat, India. Methodology: In present study, suitable sites for runoff water harvesting structures were identified using guidelines of IMSD (1995) and FAO (2003). Five criteria i.e. rainfall, land use/land cover, soil texture, lineament density and slope were selected. Thematic layers of these layers were analysed using overlay process using ArcGIS software and weights for criterias were derived with experts’ opinion using AHP. Results: Results obtained were for water harvesting site selection, AHP generated weight for criteria were 36.1%, 20.6%, 18.6 %, 13.1 % and 11.7 % for rainfall, land use/land cover, soil texture, lineament density and slope, respectively. In study area, 66.79 % area found very high suitable, 24.89 % highly suitable, 5.63 % moderately suitable, 0.88 % less suitable and remaining 1.81 % area found not suitable for water harvesting sites. As per suitability and ground truth, 24 check dam sites on scrubland, 52 check dam sites on cropland, 11 check dam sites on the river bed were obtained and 29 farm ponds sites were proposed in the study area. The result indicates that 72.27% of existing RWH sites are in very high suitability and 26.73% located in high suitable whereas only 0.49 % and 0.49 % are in the moderate suitable and not suitable area, respectively. Conclusion: To find suitable sites for runoff water harvesting experts can use remote sensing, GIS and AHP in integration for precise work.

Aims: Morphometric study of Dhatarwadi river basin. Place and Duration of Study: This study is a work done for the research work in Ph.D. degree at College of Agricultural Engineering and Technology, Junagadh Agricultural University, Junagadh, Gujarat, India. Methodology: Morphometric analysis involved determination of linear, aerial and relief aspects of the Dhatarwadi river basin, which was carried out using 30 X 30 m SRTM DEM in ArcGIS 10.5 software using standard formulae. Results: The obtained results revealed that the Dhatarwadi river basin is 6th order drainage basin. The total number of 1327 streams were identified out of which 1st, 2nd, 3rd, 4th, 5th and 6th order streams are counted as 1036, 239, 42, 7, 2 and 1 number, respectively. The mean bifurcation ratio value is 4.31 for the study area which indicates that the geological structures are not distorting the drainage pattern. Stream length ratio varies between 0.14 and 2.14 indicates late youth geomorphic stage. The length of overland flow was found as 0.3084 km which also indicates very less structural disturbance, low runoff conditions and having higher overland flow. The stream frequency of the basin is 1.5448 km-2, indicates that this basin is having high permeable geology, low relief and the almost flat topography. The form factor, elongation ratio, circularity ratio and compactness coefficient are found as 0.3951, 0.7094, 0.3126 and 1.7882, respectively of the study basin is suggests that the Dhatarwadi river basin shape is elongated. The drainage texture is 7.1426 km-1 which shows that the Dhatarwadi river basin has short duration for peak flow. The relief, relief ratio and relative ratio of the basin are found as 0.438 km, 0.009372 and 0.2352, respectively. Conclusion: All these parameters indicate that the Dhatarwadi river basin is of flat terrain with small hillocks/inselbergs having low to medium runoff potential.

A field experiment was conducted at instructional farm of soil and water engg., CAET, JAU, Junagadh during summer season (Feb.-May), 2012 to study the summer sesame response to moisture and thermal regimes with three Factorial Strip Plot Design. The crop was exposed to different thermal regimes by four dates of sowing i.e., 1 st Feb., 14 th Feb., 1 st March and 14 th March with moisture regimes by varying the irrigation interval (3, 4 and 5 days irrigation interval). Results revealed that the seasonal depth of irrigation decreased with delay in sowing from 1 st February and the growing days requirement decreased with delaying sowing after 1 st February. The more number of growing days were required to mature the crop with less total thermal heat unit. The sesame yield is significantly influenced by the thermal regimes. The highest and lowest sesame grain yield of 1131.59 kg/ ha and 555.20 kg/ha was observed for the dates of sowing of 16 th February and 1 st February, respectively. The grain yield increased rapidly by delaying the sowing from 1 st Feb. to 21 st Feb., then after it decreased slowly and continously. The vegetative stage was found the most sensitive stage to thermal regimes followed by establishment stage, flowering stage, ripening stage and reproductive stage. The highest grain yield of 991.27 kg/ha was found under drip irrigation at 3-days interval which was higher by the tune of 10.33 per cent, 17.32 per cent and 20.86 per cent as compared to that of under 4, 5 days under drip and 7-days under surface irrigation, respectively.

A field experiment was conducted at instructional farm of soil and water engineering, CAET, JAU, Junagadh during summer season(Feb.-May). The crop was exposed to different moisture regimes by varying the irrigation interval (3, 4 and 5 days irrigation interval) and mulch level (wheat straw mulch @ 5 t/ha and no mulch). It was observed that, sesame yield was significantly influenced by the thermal regimes and moisture regimes by varying water application under drip irrigation. The sesame yield response to seasonal thermal heat units as well as to stage wise thermal heat unit's availabilities could be described well by the quadratic model. The linear form of the model for the yield response to irrigation interval shows that the yield decreases with increase in irrigation interval. The developed model showed that for the 3 days and 4 days irrigation interval, the sesame grain yield increased more rapidly under mulch as compared to no mulch for the lower values of thermal heat units but for the higher values of thermal heat units, the yield decreased more rapidly under mulch as compared to no mulch. The sesame yield response to seasonal irrigation depth could be found linear indicating that the applied water was less than the crop evapotranspirations (ET c ) or the optimal water requirements and yet there is a scope for increasing the yield by increased water application.