Some key points to remember
- Empirical method of soil erosion estimation was developed by Wischmeir and Smith in 1965.
- Universal soil loss equation (USLE) i.e. A = f(RKLSCP)
- Soil loss of 20 ton/ha/year removes
a) 300 kg of OM b) 15 kg of N c) 20kg of P d) 40 kg of K
- Nitrous oxide (NO) and sulphur dioxide (SO2) are responsible for acid rain and water pollution.
- Sagarmatha and Chitwan National Park are listed in world heritage site in 1979 and 1984 respectively.
- Koshi Tappu wild life reserve declared as Ramsar site in 1987.
- Threshold velocity of soil movement: 25 km/hr
- Terrace farming reduces soil loss by 20 %.
- Department of soil and water conservation was established in 1974 AD.
- Effective root zone: Soil depth from which various crops extract the water needed for its growth.
- Water use efficiency = Y/ ET [ Y = yield and ET = Evapotranspiration]
- Lysimeter is used to measure ET.
- Water horse power: Horse power required for pumping.
i.e. WHP = QH/ 76 [ Q= discharge (l/sec.) and H = total head (m)]
or, WHP = QH/ 273 [ Q = discharge ( m3/ hr) and H = Total head (m)]
- SHP> WHP, always
- Best section of canal is semicircular and as it has less perimeter.