lecture 10 drainage

Question 1

definition of drainage

Answer 1

removal of excess surface and subsurface water to improve crop yeilds, including soluable salts

Question 2

three objectives of drainage

Answer 2

remove excess surface and subsurface water
reomve salts
maintain WT at desired level

Question 3

difference between surface and subsurface drains

Answer 3

difference is function not location

surface-removes surface water, vice versa

Question 4

four types of subsurface drains

Answer 4

tubewells
mole drain
open field drain
pipe field drain

Question 5

2 direct and 3 indirect effects of drainage

Answer 5

direct - reduction in amount of water stored
dischrage of water through system

indriect- drier soil
wetland creation
sinking of drained organic soils

Question 6

two types of drains (not talking about sub )

Answer 6

relief drains: relief an area of excess water

intercept drains: intercept water coming from outside the area

Question 7

what does steady state assume

Answer 7

water table constant with continous slow unifrom recharge

Question 8

what does transient state assume

Answer 8

wt rises instantly at event and starts to fall after

Question 9

assumptions used for drainage calculations

Answer 9

two dimensional flow
unifrom recharge
iso homo
velocity is horizontal