Irrigation as a subset of production systems and the environment

One can not simply start irrigation without also improving other production inputs (which may also be limiting crop production)

Inputs:
- Fertilizers
- Labor availability
- Markets of produce
- Pest control
- Cultivation equipment
- Drainage

Yield-water application interaction:



           Fig: General crop water production function


Shape = f (depends on soil, climate, crop type, fertility, precipitation etc.).

Law of conversion of mass:
- Water can not be destroyed or created.
- It must be accounted for with in an irrigation system or river basin.
- The only “Consumptive” or consumed portion of diverted water is evapotranspiration, or Et.

Water rights: In addition to determining the adequacy of a water sources one must also consider the effect of a diversion or change in water use on other users. Many of these users may hold a “Water right.”
A water right is a legal deed detailing the ownership of the right to divert and beneficially and consumptively use of water.

A water right usually has 3 parts:
1. Length of the time
2. Maximum rate of diversion
3. Maximum land area which can be irrigated

Unfortunately there is no overall water law, formal system of water rights or regulatory instruments for water use and allocation in Bangladesh.

Followings are available:
1. The irrigation Act (1876)
2. Bangladesh water and power development boards ordinance (1972)
3. Local government ordinance (1983)
4. Irrigation water rate ordinance (1983)

Main thing is that in practical no law is maintained and there is no monitoring.