Water is an important input for agriculture so this valuable resource is designed properly and deliverable. Reasonable information on evapotranspiration, crop water requirements, and net irrigation requirements is required for effective planning of this resource. To use optimum amount of water for crops and reduce irrigation quantity, some form of irrigation scheduling should be used by the farming community. Unscientific and injudicious application of groundwater in this region resulted in depletion of the groundwater table. To achieve effective utilization of the groundwater resources, there is a need to estimate the crop water requirement for different crops at different management levels to accomplish effective irrigation management. Crop water requirements of different crop in districts of Kutch was calculated using FAO CROPWAT 8.0 a computer simulation model. The simulation study was conducted with the objectives of determining irrigation water requirement and irrigation scheduling for some major crops. The Penman - Monteith method was used for evapotranspiration calculation in the model. The model predicted the daily, decadal as well as monthly crop water requirement at different growing stages of crops.
II. STUDY AREA
Kachchh district (also spelled as Kutch) is a district of Gujarat state in western India, with its headquarters (capital) at Bhuj. Covering an area of 45,674 km², it is the largest district of India. In Kachchh district three areas are covered in this work (Bhuj, Mundra and Anjar).
C. Soil Data
Soil type in this area is black clayey soil and loamy (medium textured). The software needs some general soil data like total available soil moisture, maximum rain infiltration rate, maximum rooting depth, initial soil moisture depletion and initial available soil moisture. Thise6 information obtained from FAO manual 56.
VI. RESULT AND DISCUSSION
It has been concluded from the study that by putting the meteorological data like Temperature (maximum and minimum), rainfall, wind speed, relative humidity, and sunshine hours into the CROPWAT model the Effective rainfall, Reference evapotranspiration, Irrigation water requirement, and Crop water requirement can be determined. CROPWAT is an easy, meaningful, and workable model for the assessment of Effective rainfall, Reference evapotranspiration, Irrigation water requirement, and Crop Water Requirement. The texture of soil from the research was black clayey soil.
From the result the average water requirement for cotton crop in Bhuj, Mundra and Anjar will be 758.8, 806.9 and 892.0 mm per decade respectively. While the irrigation water requirement will be 742.0, 791.2 and 877.5 mm per decade respectively.
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