Title 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.