Nội dung text Irrigation and Drainage Engg_ 2080 Solution-_Prepared by Ashok -[www.arjun00.com.np].pdf
Irrigation & Drainage Engineering 2080_Solution www.arjun00.com.np
© Prepared by Ashok Chaurasiya ~ 1 ~ www.arjun00.com.np 1. a) Define irrigation. List out merits and demerits of irrigation. [8] Irrigation may be defined as the process of supplying water by artificial means to agricultural fields for crop production. If water available to the plants from rainfall is not sufficient, it is supplemented by irrigation water. Merits of Irrigation: Increased Crop Yields:- Provides consistent moisture, leading to higher agricultural productivity and crop quality. Diverse Crop Cultivation: Enables the growth of a wider variety of crops, including those that require more water. Drought Mitigation:- Helps stabilize food production during dry periods, reducing reliance on rain-fed agriculture. Soil Fertility:- Facilitates the application of fertilizers and organic matter, improving soil health. Economic Stability:- Contributes to rural economies by providing jobs and increasing food supply. Demerits of Irrigation: Water Overuse: Can lead to depletion of local water resources, affecting ecosystems and drinking water supplies. Salinity Issues: Improper irrigation practices can cause soil salinization, reducing soil fertility and crop yields. Initial Costs: Infrastructure development and maintenance can be expensive. Environmental Impact: Can disrupt local ecosystems, alter natural water flows, and impact biodiversity. 2080 R/B SOLUTION IRRIGATION
© Prepared by Ashok Chaurasiya ~ 2 ~ www.arjun00.com.np b)A village of GCA as 5000 hectares of which 80% is culturable and irrigable. The intensity of irrigation for Rabi is 40% and that for Keharif is 35%. Find out the value of discharge required at head of distributary if average duty is 2000 hectare/cumec and 1300 hectare/cumec for Rabi and Kharif respectively. Solution: Gross command area (G. C. A) = 5000 hectors Culturable area (C. A) = 80% of G. C. A = 80 100 × 5000 = 4000 ha Culturable area for kharif season (Ak) = 35% of C. A = 1400 ha. Culturable area for rabi season (Ar) = 40% of C. A = 1600 ha. Duty for rabi season (Dr) = 2000 hectare cumec Duty for kharif season (Kr) = 1300 hectare cumec Then, Discharge required for kharif season, = area duty = 1400 1300 = 1.07 cumec. Discharge required for rabi season, = area duty = 1600 2000 = 0.8 cumec.
© Prepared by Ashok Chaurasiya ~ 3 ~ www.arjun00.com.np So, Taking maximum value for discharge at head of canal, Discharge of canal (Q) = 1. 87 m3 /s 2. a) Define duty and delta. Derive an relationship of duty, delta and base period. Duty (D): The area of land irrigated by unit quantity of water (1m3 /s or 1 cumecs) for the full growth period of crops is known as duty. It is always varies with crops. It is denoted by 'D' Duty can also be expressed as: Duty (D) = 8.64 × B △ Delta (△): It is define as the total depth of water required by a crop during its entire base period of the crop. It is denoted by (△). Its unit is 'm' or 'cm'. Delta (△) = total quantity of water required area of the land having the crop (ha) Relationship between duty and delta with base period : Let, B = Base period of crops. D = Duty in hector. △ = Delta. Assume, 1 cumec discharge of water is applied for base period for B days.