V. R. Desai
Assistant Professor, Water Resources Section Civil Engineering Department
Indian Institute of Technology, Kharagpur-721 302, West Bengal
Consumer oriented technological advancement/economic development is exerting a new kind of stress on the quality and availability of air and water in particular. As a result of this, the management of these natural resources has become absolutely necessary. In this paper, various strategies for better water management are discussed. Time-tested and decentralized practices of conserving water resources on a small scale as well as modern and centralized planning for big water resources projects undertaken in various parts of the world are also described. In the light of this, a few feasible short-, medium- as well as long- term strategies are suggested to improve the quality and availability of water resources for the entire human population. Through these strategies, wherein the small will complement the big; the old will complement the new, an improved water management scenario is presented over an extended space as well as time.
In terms of human necessities, water is considered most important next only to air. Food, clothing, shelter and energy are considered as next in the order of human necessities. The various ancient river valley civilizations in India, China, Israel and elsewhere prove this fact very much. It has been historically established that only these three nations and their civilizations have survived the test of time. Israel is the smallest among the three in terms of area and population, and has managed its water resources in a quite satisfactory way despite its very low rainfall. On the other hand, China is the biggest in terms of area and population and has managed its water resources to a relatively more satisfactory level despite various adverse factors. As compared to both these nations with ancient civilizations, India’s progress in water management is either satisfactory only in some sporadic pockets of geographical areas or is far from satisfactory elsewhere. The following paragraphs elaborate these observations to some extent.
Israel’s Water Management Strategies
Israel [about 20,750 sq. km. Area and an estimated population of 5.8 million in 1996]Area is a nation in the Middle East which is very important not only in terms of its history and geography but also in terms of its socio-religious composition and effective water management in spite of its limited rainfall. The average annual rainfall varies from about 150 mm in the Southern deserts to about 600 mm in the Northern hilly region. Both these values are less as compared to both the extreme values of annual rainfall in the Indian State of Rajasthan. Yet, Israel has enacted laws and implemented programmes for better water conservation and management which ensure minimization of wastage and thereby an improvement in the water use efficiency. Some of the techniques used are rainwater harvesting and drip irrigation. As a result of such practices, Israel has been able to ensure quality and availability of water for drinking and other purposes for its citizens as well as to export citrus fruits, fruit juices, wines etc., in spite of its hostile terrain with scanty rainfall [Grolier, 1997].
Chinese Water Management Practice
China is the world’s largest country in terms of population [i. e., more than 1.2 billion as per 1996 estimate] and one among the top four countries in terms of area [about 9.6 million sq. km]. The annual rainfall varies all the way from less than 250 mm in the north-west to about 2000 mm in the south and south-west. This region has more than 80% of national water resources for a national area of little more than 35% supporting nearly 55% of the nation’s population. The strong point of china is its retention of the traditional wisdom as well as adoption to modern techniques. The 1-2-1 Programme of ‘Rainwater Catchment and Utilisation’ (RWCU) provides for ‘one’ catchment area feeding ‘two’ underground storage tanks to support cash and fruit crops on ‘one’ piece of land. This as well as similar programmes have been successfully implemented in the north-western Gansu Province, and neighbouring Autonomous Regions of Ningxia Hui and Inner Mongolia. As a result of such programmes, an additional area of more than 10,000 hectares has been irrigated and an increase in agricultural yield ranging from about 20 to 100% has been achieved [Kumar, 1998]. Indian Water Management Scenario
As compared to the other two nations (i. e., Israel and China) with ancient civilisations, India is neither as compact as Israel nor as big as China in terms of area [7th in the world with little under 3.3 million sq. km] as well as population [second in the world with little under 0.95 billions in 1996]. The lower and upper bound values of the annual rainfall range are exacly the same as that of China with the minimum rainfall occurring in the cold desert of Ladhak in Jammu & Kashmir as well as in the hot desert ‘Thar’ of Rajasthan while the maximum rainfall occurring in the Western Ghats as well as in Meghalaya. For the worst scenario of water management, one can cite the instance of drought at Cherraounji-the world’s wettiest place- in Meghalaya few years ago. On the other hand, we can cite many examples of success stories – like the artificial glaciers or ‘zings’ of Ladhak in Jammu & Kashmir, the narrow wells or ‘beris’ of Jaisalmer in Rajasthan, rainwater harvesting techniques adopted in thh Chennai Metropolis of Tamil Nadu, the 300-metre deep rock tunnels or ‘surangams’ of Kasargod, Kerala, the small covered tanks or ‘kundis’ for storing rainwater in Churu, Rajasthan. All these success stories not only testify our capability to achieve water conservation, but also hint us about the grim picture that we might face in the coming years if such attempts are not undertaken on a massive scale [Joshi,1998]
In the following paragraphs, a brief outline is presented on the use of Geographical Information System (GIS) i. e., Geo-informatics and other strategies for improving water management. Other strategies for better water management are also mentioned in short.
Geo-Informatics for Simplified Storage Computation and better Water Management
Remote sensing (RS) and GIS has the potential to improve the water management, when it is adopted along with some field techniques such as constructing check dams for soil and water conservation. A simplified ‘Semi-Elliptical Cone (SEC) Model is described here.
Figure 1. Schematic of a Water Storage Created by a Check Dam Across a Stream/River
If a simple check dam is created across a stream for soil and water conservation, it will result in storage which is shown by a triangle in the Reservoir Top View in Figure 1. If such series of check dams are constructed at appropriate locations, and remotely sensed images are taken at different values of suitable time intervals (e. g., at daily or weekly intervals), we can get the areas of water storage for all the sites at those time intervals. Once such a database is created, the next thing that is required to be done is the computation of the individual as well as collective water storage volumes(V). This can be done by adopting a simplified formula, applicable for the SEC Model as given below:
V = ayz . axz . [(p/2) . (W/2) . D] . (Lf/3)
i. e., V = ayz . axz . [(p/12) . W . D . Lf](1)
ayz : Cross Sectional Coefficient (CSC)
axz : Water Spread Coefficient (WSC).
The main assumption in the SEC Model is that the water storage volume is considered to be of right elliptical half-conical shape. It means that the base of this cone is of semi-elliptical shape with half of the width (W) and depth (D) as its semi-major and semi-minor axes respectively. The vertex of this cone is the most upstream point in the Fetch direction. The coefficients CSC and WSC provide us with the representative variations in all the cross-sections considered parallel to the check dam and in all the water spread contour areas considered at all the depths respectively. Another important assumption in the SEC Model is that no tributary joins the stream or river at the reservoir area.
One can notice that Equation (1) contains a constant term, two coefficient terms and three terms corresponding to the three dimensions of the reservoir. The two coefficient terms CSC and WSC broadly depend on the longitudinal and side slope characteristics and as well as the sedimentation and erosion characteristics of the reservoir area. Among the three dimensional terms of the reservoir, fetch and width can be obtained from the RS images while depth needs to be actually measured. By properly estimating and updating the two coefficients from time to time, the storage computation can be further simplified.
On a short term as well as all-term basis such simplified storage computations can be used for modifying the elevation capacity curves as per the changed reservoir sedimentation/erosion characteristics. On a long term basis, these storage computations can also be used to complement other strategies for better water management as elaborated in the successive paragraphs.
Other Strategies for better Water Management in Indian Conditions
Uneven distribution of water resources is found almost everywhere in our country. This unevenness is spatial as well as temporal. As a result of this, it is very common to have flood as well as drought conditions existing in different parts of our country at any particular time. Nearly 75 to 80% of the annual rainfall in major portion of our country occurs during the south-west monsoon months of June to September. While the Himalayan and Sub-Himalayan regions receive water due to snow melting in summer, some regions in the north-east and the east coast receive rainfall due to north-east monsoon. Even the amount of annual average rainfall varies all the way from around 50 mm in the Ladakh region of Jammu & Kashmir to more than 11,000 mm in Meghalaya. Likewise the number of annual rainy days (with a minimum daily rainfall of 2.5 mm) varies all the way from less than 10 in Ladakh and Katch (Gujrat) to more than 150 in Meghalaya and the Western Ghat regions of Karnataka & Kerala [Rao, 1979].
Nearly a third of our country’s area is said to be either chronically drought prone area (with at least 40% probability of a maximum of 75% of the normal annual rainfall) or drought prone (with a 20-40% probability of a maximum of 75% the normal annual rainfall)[Subramanya, 1994]. It has been observed that these areas generally have an annual rainfall of less than 750 mm. In these areas scarcity of water is observed very frequently. It calls for effective water management mainly through techniques such as evaporation control and rainwater harvesting. Evaporation control is achieved by either physical or chemical or any other other techniques. Presently, the evaporation models do not lay additional emphasis on controlling measures. Under the Indian conditions the typical annual reservoir evaporation loss is of the order of 160 cm. The hydrological water balance equation based on the continuity concept [Mutreja, 1986]is as follows:
P + Ic + Ig = Q + ET + Oc + Og + Sm + Sg + Sd + L(2)
where, P : precipitation
Ic : surface inflow into basin through channels,
Q : runoff
Ig : groundwater inflow into the basin,
ET : evapotranspiration
Oc: surface outflow from basin thro’ channels,
Sm : soil moisture change
Sg : change in groundwater storage
Sd : change in depression storage and
L : loss through deep percolation. In Equation (2) above, we can improve the values of Sm, Sg and Sd by minimising Q, ET, Oc, Og and L. This is what is essentially achieved in any rainwater harvesting system. This has the capability to overcome the water scarcity situations. Rainwater harvesting is the universally recommended technique in which attempts are made to conserve rainwater wherever it falls by creating surface and sub-surface storage. Various rainwater harvesting techniques such as those through percolation pits for individual houses, permeable beds for building complexes, ponds, wells cum canals, open wells, service cum recharge wells, defunct bore wells, sub-surface storage created due to broken bricks method, cisterns, underground sumps, drinking water jars, surface and sub-surface water tanks, artificial glaciers, long underground tunnels, surface water reservoirs created by check dams and so on need to be considered as per their suitability [Ramakrishnan, 1998].
In addition to these techniques, there are other appropriate conservation practices which need to be encouraged and inappropriate depletion or wasteful practices which need to be strongly discouraged. These include:
- Educating the water users about low cost/quantity and high benefit/quality alternatives and thereby to promote a cautious utilization approach from ‘wash basin level’ to the ‘river basin level’.
- Strongly encouraging the use of rainwater of not so good quality for non-drinking purposes discouraging the ‘groundwater mining’ (i. e., over-exploitation of groundwater).
- Promoting better irrigation practices like sprinkler irrigation (even for paddy cultivation) [Sivanappan, 2000] and drip irrigation and preventing wasteful practices like flooding or furrow irrigation.
- Adopting appropriate techniques for preventing losses such as deep percolation of groundwater and thereby to ensure a favourable water balance.
Water is a very scarce commodity and unless it is properly managed, one can not avoid adverse and paradoxical situations such as temporal scarcity in above-average rainfall areas and lack of drinking water due to pollution or contamination of abundant water in general. In all such cases, there is always a scope for developing/adopting appropriate water management strategies either involving RS/GIS or otherwise which can ensure a favourable benefit-cost ratio as well as an acceptable water use efficiency. One of the shloka from the Indian Epic ‘Mahabharata’ ‘….Pranetavyam Vichakshanaih’, meaning ‘….needs intelligent control’ should serve as the guiding principle for us always and everywhere [Subramanya, 1986].
- Grolier Inc. (1997), ‘Israel’, Lands and Peoples, Volume 2, p.4-5, 104-115, Danburry, Connecticut, USA.
- Joshi, S., (1998), ‘Waterworks India’, Down To Earth, Oct. 15, p. 34-37, Centre for Science and Environment, New Delhi, India.
- Kumar, A., (1998), ‘Waterworks India’, Down To Earth, Oct. 15, p. 22-32, Centre for Science and Environment, New Delhi, India.
- Rao, K. L., (1979), India’s Water Wealth, p. 4-16, Orient Longman Ltd., Hyderabad, Andhra Pradesh, India.
- Subramanya, K., (1994), Engineering Hydrology, p. 169-172, Tata McGraw Hill Ltd., New Delhi, India.
- Mutreja, K. N., (1986), Applied Hydrology, p. 799-800, Tata McGraw Hill Ltd., New Delhi, India.
- Ramakrishnan, S., (1998), Groundwater, p. 722-734, Chennai, Tamil Nadu, India.
- Sivanappan, R. S., (2000), “Strategies in Surface and Ground Water Management’, Eighth National Water Convention, Feb. 9-11, p. 169-176, National Water Development Agency, New Delhi, India.
- Subramanya, K., (1986), Flow in Open Channels, p. VI, Tata McGraw Hill Ltd., New Delhi, India.