Water is life sustaining liquid. It is one of the most important natural resources which is essential for the existence of living organisms.
Water is the most widely distributed key resource to meet the basic needs of a growing population, social and economic ambitions, demanding agriculture, expanding urbanisation, increasing industrialisation and many other causes.
The demands for water is becoming more and more challenging day by day. Hence water in all its forms (solid, liquid and gas) should be harnessed properly.
Drinking water is one of the basic needs for all of us. Unfortunately, about 5.76 lakh villages have been facing scarcity of water. In Rajasthan, people in certain pockets have to wait for hours to collect one bucket of water from water tankers brought by the trains, trucks and tractors. In many hilly areas, the situation is the same. In many tribal and backward areas un-hygienic and unsafe water collected in ponds, tanks etc., during rainy season are the only source of drinking water.
Our country is facing frequent floods and drought often at the same time in different parts because of variable nature and uneven distribution of rains. Besides these, due to large scale deforestation and soil erosion the rivers are silted up causing floods. For sustained and increased agricultural production, industrial development and economic emancipation of the country the most vital resources are soil and water, which need to be conserved, developed and managed efficiently. In India, floods, water-logging, soil erosion, drought salty groundwater, etc. are some of the major problems of water management for agriculture and other needs.
The major problems of water management and the possible strategies of overcoming them are explained here:
Floods refer to the inundation of large parts of land by water, which otherwise remain dry for some duration of time. Flood causes heavy loss to agriculture, livestock and property. Deforestation, overgrazing, mining, industrialisation, global warming, etc. have contributed largely in the incidence of floods.
The best solution to overcome such damage is large scale irrigation projects, which will also protect from other environmental hazards. These hazards may be in the form of increase in water logging, soil sedimentation in reservoirs, damage to forest areas, large scale growth of aquatic weed of nuisance value, displacing wildlife and degradation of valuable landscape etc.
Plantations can reduce the impact of water flow on soil erosion. For water management, Land use State Boards were set-up in 1980 in order to protect the soil and water to enhance their productivity through proper land and water use practices.
A soil is said to be water logged when it is completely saturated with water, which is caused by water stagnation on flat land and low lying areas. It occurs due to excess rainfall, floods, seepage high water table, obstruction to natural drainage, over irrigation, etc.
In most of the low lying areas, wet conditions persist longer that results in delayed sowing or less crop production. Another impact is that when water dries, salts accumulate on the soil surface resulting in salinity. Since water logging is the second biggest threat to the soil, next to erosion, it is therefore, necessary to study water table fluctuations, groundwater recharge, assessment of seepage from canals, tanks, etc.
Most parts of the arid and semi-arid regions contain high percentage of sodium salts. Such water is dangerous for agriculture. Continuous use of such water results in the accumulation of sodium salts to produce Usar or alkali soil.
Some of the possible solutions to remove salinity are as follows:
i. Use of gypsum (CaSO4)
ii. Use of molasses, ash and cane sugar extracts
iii. Cultivation of salt resistant varieties
iv. Recharging with good quality of groundwater
Drought is a condition of abnormally dry weather within a geographic region.
Some solutions to overcome drought are as follows:
i. Development of additional surface water resources
ii. Direct pumping from streams, rivers and open water bodies
iii. Proper regulation of water use
iv. Increase utilization of ground water resources
v. Efficient distribution of canal water
vi. Irrigation according to requirement of crops
Rain is the main source of water on the earth. When the rainwater reaches the earth surface, a part of it is evaporated and a part of it is taken by plants, a part of ground water is retained, a part is infiltrated and the remaining water flows as surface runoff through drainage systems into the sea. Each of the river system has separate drainage units which depend upon the terrain, geology, climate and land use pattern.
In order to tackle the problems of water resources and various forms of degradation and to develop these resources for sustained and increased productivity in the regions it is essential to focus our attention to natural drainage units called the watershed (Fig. 15.2). Watershed is defined as ‘land area that delivers water, sediment and dissolved substances through small streams to a major stream (river)’.
The management of a single unit of land with its water drainage system is called watershed management. This technique has several components which includes soil, water and vegetation cover. The natural drainage pattern of a watershed unit, if managed properly, can bring about a year-round supply of water.
There are two main steps of its conservation:
1. Construction of many long trenches and mounds along the contours of the hill to hold rainwater and allow it to percolate into the ground. This ensures that underground reservoirs are fully recharged. This is followed by growing of grasses and shrubs which hold the soil firmly.
2. The second step is to form nala plugs in the streams, so that water is held in a stream and does not rush down the hillside.
The proper management of watershed is to maintain the water yield confined to the drainage so as to derive maximum benefits and sustained productivity by proper land-use and suitable cropping patterns. The various conservation and crop management practices should be adopted in such a way that loss of soil, as well as moisture, is minimized.
The main objectives of soil and water conservation are as follows:
i. To conserve these resources in the upper catchments by providing suitable vegetation cover to protect soil erosion and to prevent the silting of river channels and the reservoirs, which prevent the flood.
ii. In case of cultivated areas, the conservation measures are different and depend on agricultural practices, economics and other aspects.
Other conservation measures undertaken for watershed management are as follows:
These include land leveling, shaping, contour bunding, terracing, grading of land, bank protection, check-dams, etc.
These include protection by vegetation, such as grass cover, pasture development, contour farming, strip-cropping, crop rotation, etc.
Under this, plantation is done, while overgrazing and forest fires are controlled.
Integrated Watershed Management:
In recent years watershed management has received wider acceptance.
It incorporates several diversified programmes, such as:
i. Amendment of alkali and acid soils
ii. Control of shifting agriculture
iii. Creation of State Land use Survey Organisation
Indian Space Research Organisation (ISRO), National Remote Sensing Agency (NRSA), Food and Agriculture Organisation (FAO) and United Nations Development Programmes (UNDP), have taken more initiatives for soil and land use survey and for planning of soil conservation programmes. Awareness was created to develop, conserve and manage the land in the wider perspective in the various sectors. It is, therefore, considered necessary to have some high level body where all matters related to soil and water resources could be discussed under one platform.
The Ministry of Agriculture, Government of India, has set up State Land use Boards under the chairmanship of Chief Minister of States, to take up all matters about the natural resources their utilization and degradation of land. The Government of India has launched an integrated watershed management in the catchments of flood prone rivers with the collaboration of NRSA and ISRO.
Old people said ‘capture water when it rains’. It is also true in the present context of water crisis. Today, the world is facing serious water shortage. Every drop of water is valuable because ‘where there is water there is life’. There has been increased aridity in India over the last few decades. Water scarcity is likely to increase in India due to increasing population. Under extreme conditions in future, human society will be bound to use different means of adaptation due to climatic changes.
Objectives of Rainwater Harvesting:
1. To reduce loss from surface runoff
2. To avoid flooding
3. To meet the increasing demands of water
4. To raise the water-table by recharging groundwater
5. To reduce groundwater contamination
Need for Rainwater Harvesting:
Why does rainwater need to be harvested? It matters more today than any other time in the past.
There are following reasons:
1. About 50% fresh water goes waste due to runoff.
2. More than 1 billion people lack clean drinking water globally.
3. Population increase is much faster than the increase in the amount of available fresh water.
4. Per capita availability of fresh water will further decrease in the coming years.
5. During summer and droughts, it will supplement the domestic water requirement.
6. Climatic changes also lead to increase in precipitation, evaporation, transpiration, occurrence of storms and changes in biogeochemical processes affecting water quality.
7. It is essential to reduce groundwater pollution and improve the quality of water.
8. It is a better option for providing clean and safe water particularly for drinking and other domestic uses (Table 15.3).
Rainwater Harvesting Technology:
Rainwater harvesting is the method of storing rainwater and thereby increasing the recharge of groundwater. As India since the very beginning was primarily an agricultural country, the need to harness water was felt. This is also due to fact that rainfall in our country occurs only for two to three months; therefore, water needs to be conserved for its use throughout the year. Even the ancient civilizations like Harappa, Mohenjo-Daro, etc. provide excellent examples of water harvesting through a network of tanks and reservoirs. Some of the old forts like Jaigarh Fort near Jaipur and Fatehpur Sikri near Agra, also provide good examples of water storage through rainwater harvesting.
Several techniques are in practice to recharge groundwater. One method is to manage rainwater in such a way that it is used at the source. If as much water as possible is collected and stored, it can be used after the rainy season is over. This method has been traditionally practiced in dry areas. Simple local techniques such as ponds and earthen embankments can help in the harvesting and storage of rainwater. Rural and urban water use, restoration of streams for recreation, fresh water fisheries and natural ecosystems, etc. need rainwater harvesting. Local practices for rainwater harvesting can provide sufficient amount of water.
One hectare of land in an arid region with 100 mm rainfall annually could yield one million litres of water per year through rainwater harvesting.
Deep wells may provide a source of clean water, but it is possible only in the rural areas. Traditional systems could become more efficient if scientific attempts are combined to enhance their productivity. Other methods are refilling of dug-wells, recharging of hand pumps, construction of percolation pits, trenches in the agricultural fields, bunds and check-dams etc. (Fig. 15.4). The above practices have been used since long in India. Now there are advanced techniques of water harvesting systems such as canals, tanks, embankments and wells.
In hilly areas, rainwater harvesting has been practiced in rooftops and springs with the help of bamboo pipes. In arid and semi-and regions, wells and step-wells were constructed to tap groundwater. Construction of tanks has been a very popular method in recent years to conserve rainwater.
Rainwater harvesting treatment is very important in the areas where pollution is alarming. It is now possible to use nano-filtration for the removal of hardness, natural organic materials, pesticides, bacteria, viruses, salinity, nitrates, arsenic and other pollutants. Weather and water policy should be integrated and may be streamlined to promote rainwater harvesting in the water stretched regions of the world. In the urban areas, water resources are fast depleting due to population increase and unrestricted use of water.
Modern Rainwater Harvesting:
Availability of water has become a major problem in the urban areas due to high density of population. In many cities, water is available only for an hour or so and that too in a trickle. The urban areas are mostly dependent on groundwater due to which its level is falling day by day. The problem is further compounded by the fact that most of the urban land is covered by concrete structures making hindrance to groundwater recharge.
To overcome this problem, rooftop rainwater harvesting has proved to be an effective method. In this method, the rainwater falling on rooftops, which otherwise flows down the drain, is diverted to an underground tank for future use. Rainwater can also be diverted to dug-wells or pits for recharging groundwater (Fig. 15.3). In Rajasthan, tremendous work has been done by Sri Rajendra Singh to collect rainwater by constructing check-dams. He was awarded the Magasaysay Award for his commendable work.
Top 10 Water-Rich and Water-Poor Countries:
Iceland, Surinam, Guyana, Papua New Guinea, Gabon, Solomon Islands, Canada, Norway, Panama and Brazil.
Kuwait, Egypt, United Arab Emirates, Malta, Jordan, Saudi Arabia, Singapore, Moldavia, Israel and Oman.