Mokama Taal An Ephemeral Lake Requiring Holistic Management

Transcription

1 Sengupta, M. and Dalwani, R. (Editors) Proceedings of Taal2007: The 2 th World Lake Conference: Mokama Taal An Ephemeral Lake Requiring Holistic Management C.P. Sinha 02, Jairaj Vasundhara, East Boring Canal Road, Patna (India) c_p_sinha@rediffmail.com ABSTRACT Mokama Taal (Lake) is located in Central Bihar (India). It is ephemeral in nature. It comprises a group of seven continuous taals. It is spread over a vast area and acts as a delta to several rivers that flow into it. Most of the area remains submerged under 4 to 6-metre deep water during monsoon and cultivation of rainy season crops over it is not possible. Even cultivation of winter season crops suffers if the drainage and reclamation of the area get delayed beyond sowing time (5 October). This is considered to be the main problem. A number of schemes have been executed to solve this but without any substantial success. The rich biodiversity and biological resources have not been given due attention and multiple uses of various resources have not been attempted. The problem has not only technical and economic aspect but also environmental and sociological dimensions. People are found not very receptive to governmental actions. Their involvement in holistic management will certainly ensure sustainable development. Keywords: agriculture, biodiversity, holistic participatory management, sustainability. INTRODUCTION According to the Ramsar Convention (97), wetlands are areas of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres. They support disproportionately large part of human population and fulfil a wide range of essential functions that help sustain plants and animals as well. However, their significance has not yet been fully understood and appreciated. Wetlands are generally considered to be wastelands. They are often drained and reclaimed for agriculture or urban expansion. The sooner this trend changes, the better it will be for the society. Mokama Taal (Lake), located in the central region of the Bihar state of India is unique in many respects. It is vast in expanse and ephemeral in nature. The area gets submerged under deep water during monsoon period and becomes unfit for cultivation of kharif crops (grown during April to September). Cultivation of rabi crops (grown during October to March) also suffers in productivity if drainage of the area is not complete by their sowing time (5 October). The Government has executed a number of schemes and some more are in planning stage for draining out water from the taal and reclaiming land for agriculture. The strong farmers lobby has been influencing policy making and planning with the result that the focus remains only on agriculture and other aspects of development are lost sight of. The taal exhibits enormous biodiversity. Its biological resources are rich and diversified. It has already been enlisted as an Important Bird Area by Indian Bird Conservation Network. This aspect has not been given due importance and attention. No scientific information on the state of environment of the taal is available. It is now highly desirable that all aspects of development should be addressed and holistic management approach should be adopted. Description of the Study Area The so called Mokama Taal is not just one single taal but a group of seven taals covering an area of,062 square kilometres and the width varying from 6.5 to 7.6 kilometres. It has very unique features. It is a saucer shaped depression running along the right bank of the river Ganga. Though the taal is continuous, it is named differently in different reaches from west to east as Fatuha Taal, Bakhtiarpur Taal, Barh Taal, More Taal, Mokama Taal, Barahiya Taal and Singhaul Taal. It lies in the lower Kiul- Harohar basin situated between latitudes 24 0' N and 25 30' N and longitudes 84 40' E and 86 30' E. The river Harohar, known as Dhowa and Mohane in upper reaches and running from west to east, is the master drain of the taal area. The land between the Ganga and the taal area is rather high and natural drainage across the land is not possible. The northern strip of the taal, therefore, drains from north to south, the ground drainage slope is very flat, varying from 0.6 to 0. metre per kilometre, from west to east and there is a cross slope from south to north. Several rivers that rise in the hills on the south flow northward and join the river Harohar flowing in the valley of the taal area (Figure ). These rivers are aggrading in several reaches. The taal area acts as a delta for these rivers.

2 The rivers flowing from the south through the taal are generally rainfed and carry very little discharge during non-monsoon period. However, during monsoon months the flood peaks caused due to heavy rains pass quickly through the upper region of the river system having steep gradient and accumulate in lower region (taal area) where the gradient is mild. Further, flood water from the Ganga also finds its way in the taal and completely stops drainage out of it. The flooding is more acute when the Ganga remains in spate for long duration and 75% to 00% of the taal area gets submerged. The maximum depth of the submergence in the recent past was recorded in 987 which varied from 3.86 metres in Fatuha Taal to 5.76 metres in More and Mokama taals. The total combined capacity of the taal at the highest flood level (average metres above mean sea level) is million hectaremetres (SBSIC 994). The biological resources of the taal area are rich and diversified. They can very well sustain the avian community. It exhibits enormous biodiversity. About 49 species of birds have been estimated to occur in the area. Further surveys may surely add to the number. The site holds, on a regular basis, over 20,000 breeding and migratory waterfowls. Some globally threatened and near threatened species are also found here (Mishra et al 2004). There is scope for commercial fisheries, production of macrophytic biomass for meeting demands of fuel and fodder, establishment of cottage industries, development of bio-energy and bio-fertilisers apart from avenues for land based employment opportunities (Roy 200). Statement of the Problem Due to continued submergence of most of the taal area, which is surrounded by agricultural fields from July to September, kharif cultivation is not possible on vast area. Rabi cultivation is based on residual moisture of the land freed from submergence. If somehow drainage of the taal is delayed beyond 5 October, rabi sowing is delayed and the crops suffer due to loss of moisture when they approach the state of maturity because the required irrigation facility is not available. This is the main point of concern for the planners. Kharif, rabi and hot weather crops are grown over 30.30%, 65.54% and 4.6% area respectively (SBSIC 994). The total catchment area of various rivers draining into the taal is 3,340 square kilometres and with a moderate runoff of 5 centimetres the incoming water from the catchment can appreciably submerge the taal area. The entry of backwater of the Ganga in the taal is another major cause of flooding. However, the possible reasons of water logging of the taal are schematically presented in Figure 2. Figure. Index map of Mokama group of Taals - 587

3 Subsystem Contributing Factor Causes of water logging Natural Channel Carrying capacity Spilling of back flow Due to low carrying capacity of channels water spills in taal area Inundation by the Ganga by back flow through the Punpun Valley lines By Ganga by back flow through the valley lines joining the taal Bed slope Moderate bed slope of rivers in taal area reduces the flow Land Topography Relief Low lying pockets in taal area High gradient in upper catchment of taal area Water logging in Mokama Taal Cropping Pattern Water Management Cropping Pattern Low withdrawal of ground water in taal area Unsuitable cropping pattern Rainfall 85% of average annual rainfall occur in 3-4 months Hydrology Runoff High runoff from catchment Ground Water High ground water table Percolation Low percolation from taal soils Land development Road, rail, bridge etc across natural river Developmental Activities Irrigation System Underutilisation of ground water in the taal area Drainage channels May be inadequate in number Figure 2. Possible Causes of Water Logging in Mokama Group of Taals 588

4 Paradoxically the taal area suffers from the two extreme problems of flood and famine: the former due to inadequate drainage and the latter due to delayed drainage and lack of irrigation facility. The area has only rabi crops and the productivity is generally adversely affected. Planning of development of the resources is based on this consideration and other uses of water and conservation of avian population are not given due attention. Although trapping and shooting of birds are prohibited by law, these activities go on. Poisoning of waterfowls with pesticide using rice as bait is also becoming a common modus operandi to catch birds (Mishra et al 2004). Development Plans The main objective of all the development plans for the taal area thought of so far at various governmental levels has been to maximise agricultural production by increasing area under cultivation and creating irrigation facilities. Under the Mokama Taal Drainage Scheme, Phase I, seventeen channels from local depression to the main outlet channel (the Harohar) were renovated during Dr K.L. Rao, the then Union Minister of Irrigation and Power, visited the taal area in August 970 and July 972 and suggested construction of embankments on the right side of the Punpun and both banks of the Harohar to check the Ganga water entering the taal, parallel drain in the upper reach to divert flows of various rivers and some other measures. Incidentally the present Government of Bihar is also thinking to construct a link channel in the upper reach of Kiul-Harohar basin. A high-level technical committee headed by Mr. C.C. Patel, the then Secretary (Water Resources), Government of India, inspected the site in February 976 and suggested some long-term and short-term measures including construction of reservoirs in the upper catchments, drainage channel on the southern periphery, soil conservation measures and contour bunding, prevention of entry of the Punpun and Ganga waters into the taal area. The Ganga Flood Control Commission prepared a report on the Comprehensive Plan of Flood Control for the Kiul-Harohar River System in 987 which incorporated the suggestions already made and in addition suggested to explore the possibility of using the taal area as a natural flood detention basin for moderating the flood flows of the Ganga. The Mokama Taal Technical-cum- Development Committee headed by Mr. N. Sanyal submitted its report in March 988 and recommended adoption of all measures suggested earlier in toto or in modified form and also noted the availability of large range of water resistant varieties of kharif crops which could be introduced through demonstration. The committee also suggested greater attention to tubewells and lift irrigation from the Ganga. The Task Group constituted by the Planning Commission reviewed the whole situation and besides other recommendations suggested construction of check dams, channel improvement and conjunctive use of surface and ground waters (Task Group 999). The Monitoring Team of the Central Water Commission suggested raising and strengthening of 74 zamindari bundhs (embankments constructed by big land owners) and renovation of 63 existing pynes (distributaries). The total length of such bundhs is kilometres which benefit 9,846-hectare area (CWC 2007). The Indian Council of Agricultural Research constituted a team which suggested contingency plan and long-term strategy. They endorsed most of the engineering measures recommended earlier and in addition suggested crop diversification, zero tillage, pest management, integration of crops, horticulture, trees, fisheries and livestock etc (ICAR 2003). A management model was developed by the National Institute of Hydrology on the assumptions of no overflow from the Punpun and no backwater entry from the Ganga to the taal area. The objective function used was as follows: Maximise f(cropped Area) = Maximise m i= m n n2 SBAKij + TAKj + n2 i= SBARij + TARj in which m = number of sub-basins in the upper catchment (Kiul-Harohar basin). n and n2 = number of crops grown in kharif and rabi seasons respectively. SBAKij = area of ith sub-basin allocated to jth crop in kharif season, square kilometres. TAKj = Taal area allocated to jth crop in kharif season, square kilometres. SBARij = area of ith sub-basin allocated to jth crop in rabi season, square kilometres. TARj = Taal area allocated to jth crop in rabi season, square kilometres. The objective function in the above model was subjected to various constraints related to storage, area, water requirement, affinity and cropping pattern. There were 09 variables and 45 constraints out of which 39 were linear and 6 non-linear in nature. The model was solved using Quantitative Systems for Business software. The results quantitatively indicated that by increasing the storage in the upstream catchment the waterlogged area in the taal could be substantially decreased and irrigation potential increased (NIH 2000). This model also does not take requirements other than those of agriculture into consideration. n 589

5 Holistic Management Development of the taal area with a view to maximising agricultural production has been in focus for the last more than five decades, but no substantial progress is visible on the grass root level. The natural flooding and draining system as existing 5-20 years back is wanted to be restored by local farmers. They are not much receptive to new cropping pattern. The main crops of gram and lentil are severely affected by cutworm and podborer almost every year. The problem is further aggravated when sowing is delayed. Proper pesticide management is not being practised (ICAR 2003). What has been attempted and done so far is obviously draining and reclaiming land in the taal area with the sole objective of bringing the same under agriculture. Other aspects of developing available water and land resources for various other uses have not been given due attention. Reckless exploitation of croplands for agriculture, and indiscriminate uses of chemical fertilisers and pesticides have adversely been affecting the faunal diversity in the taal area. Fortunately, the avian fauna have now begun to colonise in this area. When the birds get disturbed at the nearby Kawar lake, they fly to Mokama Taal. As such Mokama Taal may be developed and managed for culture of water resistant paddy and other crops along with integrated culture of air-breathing fishes and shell fishes for increasing bio-diversity. Such technology will provide suitability for sustaining the bird population in this region. Ecological requirement of different species of birds and assessment of bird-plant specific relationship may be made in order to develop conservation and management strategies (Roy 200). It is highly imperative that a holistic management approach is adopted for the taal area and its land and water resources are developed and managed not only for agriculture but also for meeting other requirements related to environment and ecology. Then only the measures will prove to be sustainable. A scientific study should be made for framing the strategy and local people may be fully associated and involved in policy making as well as implementation and management. Such an approach is bound to bring success in full measure. CONCLUSION Mokama Taal is a unique ephemeral lake. It is under constant exploitation for agriculture. Other aspects for development for maintaining ecological balance is not given due attention and importance. Holistic management of the taal is highly imperative. REFERENCE CWC. (2007) Report on Raising and Strengthening of Zamindari Bundhs and Residual Work of Pynes in Mokama Taal Area (Bihar), Monitoring Directorate, Central Water Commission, Government of India, New Delhi, total pages 6. ICAR. (2003) Report on ICAR Team Visit to Mokama Taal, Indian Council of Agricultural Research, New Delhi, total pages 32. Mishra, Arvind; Alam, Mahboobi; Hussain Ali; and Roy, S.P. (2004) Mokama Taal Wetlands (Barh) Important Bird Areas in India Priority Sites for Conservation, Indian Bird Conservation Network, Bombay Natural Society, Bird Life International (U.K.), total pages 33. NIH. (2000) A Management Model for the Water Logging and Drainage Congestion Problem of Mokama Group of Taals, National Institute of Hydrology, Roorkee, total pages 64. Roy, S.P. (200) A Personal Communication to Mr. Arvind Mishra, total page. SBSIC (994) Report of Second Bihar State Irrigation Commission, Volume V, Part II, Government of Bihar, Patna, total pages 06. Task Group. (999) Report on the Drainage Problem in Mokama Group of Taals, Planning Commission, Government of India, New Delhi, total pages