Water conservation Techniques

Primary source of water in India is south-west and north-east monsoons. Monsoon, however, is erratic and as you have already studied the duration and the amount of rain fall is highly variable in different parts of our country. Hence, surface runoff needs be conserved. The techniques for conservation of surface water are:

(a) Conservation by surface water storage

Storage of water by construction of various water reservoirs have been one of the oldest measures of water conservation. The scope of storage varies from region to region depending on water availability and topographic condition. The environmental impact of such storage also needs to be examined for developing environment friendly strategies.

(b) Conservation of rain water

Rain water has been conserved and used for agriculture in several parts of our country since ancient times. The infrequent rain if harvested over a large area can yield considerable amount of water. Contour farming is an example of such harvesting technique involving water and moisture control at a very simple level. It often consists of rows of rocks placed along the contour of steps. Runoff captured by these barriers also allows for retention of soil, thereby serving as erosion control measure on gentle slopes. This technique is especially suitable for areas having rainfall of considerable intensity, spread over large part i.e. in Himalayan area, north east states and Andaman and Nicobar Islands. In areas where rainfall is scanty and for a short duration, it is worth attempting these techniques, which will induce surface runoff, which can then be stored.

(c) Ground water conservation

Attributes of groundwater

• There is more groundwater than surface water.

• Groundwater is less expensive and economic resource and available almost everywhere

• Groundwater is sustainable and reliable source of water supply.

• Groundwater is relatively less vulnerable to pollution.

• Groundwater is a free of pathogenic organisms.

• Groundwater needs little treatment before use.

• There is no conveyance losses in underground based water supplies.

• Groundwater has low vulnerability to drought.

• Groundwater is the key to life in arid and semi-arid regions.

• Groundwater is source of dry weather flow in some rivers and streams. As highlighted earlier, out of total 4000 BCM (billion cubic meters) precipitation that occurs in India, about 45 mhan (million hectares meters) percolates as ground water flow. It may not be possible to tap the entire ground water resources. The ground water potential is only 490 BCM. As we have limited ground water available, it is very important that we use it economically and judiciously and conserve it to the maximum. Some of the techniques of ground water management and conservation are described below.

(i) Artificial recharge

In water scarce areas, there is an increased dependence on ground water. The water table declines quickly due to low and erratic rainfall. The only alternative is to replenish the ground water by artificial means. As you have studied in the previous lesson, there are various techniques to develop and manage ground water artificially. In one of the methods, water is spread over ground to increase area and length of time for water to remain in contact with soil. So as to allow maximum possible opportunity for water to enter into the ground. Try to recollect the other methods of recharging ground water.

(ii) Percolation tank method

Percolation tanks are constructed across the water course for artificial recharge. The studies conducted in a Maharastra indicates that on an average, area of influence of percolation of 1.2 km2, the average ground water rise was of the order of 2.5 m and the annual artificial recharge to ground water from each tanks was 1.5 hec m.

(d) Catchment area protection (CAP)

Catchment protection plans are usually called watershed protection or management plans. These form are an important measure to conserve and protect the quality of water in a watershed. It helps in withholding runoff water albeit temporarily by a check bund Constructed across the streams in hilly terrains to delay the run off so that greater time is available for water to seep underground. Such methods are in use in north-east states, in hilly areas of tribal belts. This technique also helps in soil conservation. Afforestation in the catchment area is also adopted for water and soil conservation.

e) Inter-basin transfer of water

A broad analysis of water and land resources and population statistics of various river basins in our country reveals that areas in western and peninsular regions have comparatively low water resources/cultivable land ratio. Northern and eastern region which are drained by Ganga and Brahmaputra have substantial water resources. Hence, the scheme of diverting water from region with surplus water to water deficit region can be adopted Ganga- Cauveri link would enable to transfer of vast quantities of Ganga basin flood water running out to sea, to west and south west India. The transfer of the surplus Ganga water would make up for the periodical shortage in Sone, Narmada, Godaveri, Krishna and Cauveri. The National Grid Commission envisages diversion of part of the surplus discharge in the Ganga near Patna during the high flood period.

(f) Adoption of drip sprinkler irrigation

Surface irrigation methods, which are traditionally used in our country, are unsuitable for water scarce areas, as large amount of water is lost through evaporation and percolation. Drip irrigation is an efficient method of irrigation in which a limited area near the plant is irrigated by dripping water. It is suitable method for any area and especially for water scarce areas. This method is particularly useful in row crop. Similarly sprinkler method is also suitable for such water scarce areas. About 80% water consumption can be reduced by this method, whereas the drip irrigation can reduce water consumption by 50 to 70 %.

(g) Management of growing pattern of crops

In water scarce areas, the crop selection should be based on efficiency of the crop to utilize the water. Some of the plants suitable for water scarce areas are (i) Plants with shorter growth period; (ii) High yielding plants that require no increase in water supply; (iii) Plants with deep and well trenched roots and (IV) Plants which cannot tolerate surface irrigation.

(h) Reducing evapotranspiration

Evapotranspiration losses can be reduced by reducing the evaporation from soil surface and transpiration from the plants, in arid zones, considerable amount of water is lost in evaporation from soil surface. This can be prevented by placing water tight moisture barriers or water tight mulches on the soil surface. Non-porous materials like papers, asphalt, plastic foils or metal foils can also be used for preventing evaporation losses. Transpiration losses can be reduced by reducing air movement over a crop by putting wind breaks and evolving such types of crops which possess xerophytic adaptations.

(i) Reducing evaporation from various water bodies

The quantity of water lost through evaporation is very high in many areas in our country. It is estimated that 10000 hectares of land loses about 160mm3 of water each year. The water losses through evaporation from storage tanks, reservoirs, irrigation tanks, rivers and canals reduce the water available for various uses. The methods that reduce evaporation from water bodies are- installing wind breaks, reducing energy available for evaporation, constructing artificial aquifers, minimizing exposed surface through reservoir regulation, reducing ratio of area/volume of water bodies, locating reservoirs at higher altitudes and applying monomolecular firms.

(j) Recycling of water

The wastewater from industrial or domestic sources can be used after proper treatment, for irrigation, recharging ground water, and even for industrial or municipal use. If agricultural lands are available close to cities, municipal waste water can be easily used for irrigation.

Micro Irrigation

Drip irrigation, also known as trickle irrigation or micro irrigation, functions as its name suggests. Water is delivered at or near the root zone of plants, drop by drop. This method can be the most water- efficient method of irrigation, if managed properly, since evaporation and runoff are minimized. In modern agriculture, drip irrigation is often combined with plastic mulch, further reducing evaporation, and is also the means of delivery of fertilizer.

Major, Medium, Minor Irrigation

Irrigation works have been classified as major, medium and minor, depending on their culturable command area.
1. Major Irrigation: Culturable command area (CCA) more than 10,000 hectares.
2. Medium Irrigation: Culturable command area more than 2,000 hectares but less than 10,000 hectares.
3. Minor Irrigation: Culturable command area up to 2,000 hectares.

All groundwater and surface water schemes having culturable command area upto 2000 ha individually are classified as minor irrigation schemes. Minor surface water flow irrigation projects comprising storage, diversion works and surface lift irrigation schemes occupy a prominent place in the scheme of irrigated agriculture particularly in the undulating areas south of the Vindhyas and the hilly regions. Minor Irrigation Schemes are labour intensive, provide employment to rural population and check their migration to urban areas. They also help in raising the standards of living of rural population and bring them above the poverty line. Such schemes are quick maturing and the benefit from the schemes starts flowing with a very small gestation period. Generally, the schemes are installed in a maximum of two to three years.

The minor irrigation schemes are funded from plan funds, institutional finance and private investments by the farmers. It is generally considered as a people’s programme as the plan funds form only a small portion of the total investment for its development.

Institutional investment for minor irrigation

Institutional finance plays an important role in the implementation of Minor Irrigation schemes. The Land Development Banks, State Cooperative Banks, Commercial Banks and NABARD provide credit facilities to the farmer and institutions for development of Minor Irrigation facilities. Institutional finance by NABARD for minor irrigation schemes has been decreasing over the last 3 years. The total credit refinanced by NABARD for minor irrigation has decreased from Rs.795.32 crore in 1995-96 to Rs.477.91 crore in 1997-98. In addition, the institutional investment being provided under the normal programme by the Land Development banks/cooperative banks has decreased from Rs.37.29 crore in 1995-96 to Rs.10.72 crore during the year 1997-98.

In order to find out the reasons for decline in credit disbursement, a meeting was held on 12th July, 1999 in the Ministry of Water Resources. During the meeting it was pointed out by several cooperative banks that the meetings of the Unit Cost Committee set up by NABARD are not held on regular basis. Since the unit cost has not been revised, the lending for minor irrigation sector has reduced. It was also pointed out that in many cases the ground water availability report, as given by State Ground Water Board, is not updated but in several cases found to be inaccurate. It was decided that as the Central Ground Water Board is operating more that 13000 observation wells in the country and the Board regularly conduct a studies regarding water availability as well as its behaviour in different parts of the country. The same may be used for the purpose of providing financial assistance for the minor irrigation sector. It was also noted that late approvals by NABARD contribute towards delaying grants of credit for minor irrigation sector. There was a general consensus that the eligibility conditions for institutional finance for minor irrigation should be less restricted. There has been a decline in institutional finance due to persisting default by some States as the recovery level, is very low in these States. The Ministry of Water Resources is taking steps to remove the above problems and ensuring that the credit disbursement provided by NABARD and State cooperative banks for minor irrigation sector does not decline.

The salient features of Minor Irrigation Programme are:

To ensure adequate provision of funds for the externally aided projects according to the schedule of disbursement;

To ensure prioritisation for on-going schemes;
Stepping up the institutional investment to the extent possible including subsidy to small & marginal farmers and other weaker sections;
Stepping up ground water development, especially in the Eastern and North- Eastern States;
Encouraging minor irrigation programme for tribal, backward, drought-prone areas and areas having pre-dominantly scheduled caste and scheduled tribe farmers by establishing effective coordination as well as by dovetailing if possible all ongoing programmes/schemes like employment generation schemes etc. under various Ministries.
Encouraging schemes utilising non-conventional sources of energy like hydrums etc.,
In water scarce and drought prone areas, the use of sprinkler/drip irrigation system as a water saving device as well as for efficient use of water for productivity should be encouraged.
To improve the utilisation of public tube wells and their rehabilitation along with turning over to beneficiary farmers for O&M.
Whereas major and medium irrigation works are meant for tapping surface water (e.g., rivers), minor irrigation mainly involves ground water development, e.g., tube-wells, boring works, etc.

Drainage:

Removal of excess water from the surface or below the surface of the soil so as to create favourable conditions for plant growth.

Causes of Water Logging

a. Intensive rains

b. Floods

c. Soil slope

d. Bunds

e. Defective irrigation

f. Seepage from unlined canals.

Effects of ill drained conditions

a. Lack of accretion of soil.

b. Restricted root growth and lodging problems

c. Difficulty in tillage.

1. Increase in salinity in top layers of soil. All crops including rice require well drained conditions. Crops like maize mustard are very sensitive to water logging or ill drainage even for a short Period. Mid-season drainage is important in rice.

2. Drainage can be surface drainage (or) Sub surface drainage.

Benefits of drainage

1. Helps in soil ventilation/accretion

2. Facilitates timely tillage operations.

3. Better and healthy root growth.

4. Favours growth of soil microorganism (better mineralization)

5. Warming up for optimum soil temperature maintenance.

6. Promotes leaching and reduce logging.

7. Improves anchorage and reduce lodging.

8. Improves soil structure and decrease soil erosion.

9. Improves sanitary and health conditions and makes rural life happy.

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