what is the source of groundwater? explain your answer. State any five use of water
Answers
Explanation:
In each irrigation area there is a demand for water and a supply of water. The demand for water varies over time and depends on the types of crops, crop growth stages and on the climate (see Training Manual 3). While transporting irrigation water from the water source and applying it to the plant roots, a portion of the water is lost through evaporation, leakage from the canals and percolation below the roots of the crop. The scheme's gross irrigation need, SINgrossincludes these water losses. To express the percentage of irrigation water that is used efficiently and what percentage is lost, the term irrigation efficiency is used. See also Annex I in Training Manual 4.
The supply of water to the irrigation system, SWS, should be almost if not equal to the demand for water, SINgross, which is the total of the irrigation need for all fields plus the water loss (see Figure 1) during transport and distribution.
Figure 1 - SWS must equal the SINgross
When the supply of water exceeds the demand, plants may receive too much water which has a negative effect on their growth. Or, on the other hand, costly water may be spilled and disappear into the drainage system. When the supply is less than the demand, the irrigation area may suffer from drought and plant production will decrease.
Extension agents and field technicians need to be able to advise farmers on how to handle existing as well as anticipate future problems of water shortage. Problems may arise when an irrigation area is extended, or when new crops are introduced. The technician therefore needs to have an understanding of water shortage problems together with a knowledge of the correct approach, albeit simplified, to matching the supply with the demand for water. This chapter deals with the supply aspects of irrigation. Various types of water sources are presented which are largely what determine water availability. River and groundwater hydrology are beyond the scope of this manual, so that only a conceptual example is provided.
2.1.1 Water sources
The water needed to supply an irrigation scheme is taken from a water source. The most common sources of water for irrigation include rivers, reservoirs and lakes, and groundwater. Figure 2 shows a bird's-eye view of different irrigation water sources.
Figure 2 - Schemes irrigated from different water sources
2.1.2 Water availability
The possibility of supplying as much water to the irrigation area as is needed during each period of the irrigation season depends primarily on the availability of the water at its source. Availability may vary a lot over the year, or even between one year and another. Secondly, the supply depends on the capacity of the facility installed to withdraw the water from the water source. Further, technicians should be aware that water must be available during each week or month of the growing season. This is illustrated with an example.
It is thus important to know how much water one can tap from a given water source over the course of a season or a year, when:
- developing a new irrigation scheme,
- extending an existing scheme,
- changing the cropping season,
- adding a second or third irrigation season,
- switching from a low water demand crop to a crop such as rice with high water requirements.
Answer:
Most groundwater originates as meteoric water from precipitation in the form of rain or snow.
The most common water uses include:
Drinking and Household Needs.
Recreation.
Industry and Commerce.
Agriculture.
Thermoelectricity/Energy.