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agricultural use. Water conservation through storage of excess rainwater during the monsoon and surface flow in the existing low areas, canals and smaller rivers is possible. Cultivation of irrigated second crop with the stored water during the winter/dry season can change fate of the coastal people. Excavation of ponds and re-excavation of existing canals will increase storage capacity for subsequent use of water for irrigating the second crop. New ponds and re-excavated canals can also be used for fish cultivation. Fish cultivation alone in the ponds and re-excavated canals will be cost effective. Rainfall contributes a significant portion of water requirements for most crops in Bangladesh, even in most of the irrigation projects especially during the monsoon. But rainfall is unpredictable and sometimes uncontrollable at the field level beyond certain amount in a day or a week. Often excess rainfall drains out of the command area of the irrigation systems or crop fields. Rainfall can be more beneficially utilized if storage or pump suspension can adjust irrigation deliveries for maximum use of rainfall. In field conditions, effectiveness of rainfall is more important than the total amount of rainfall for a day, week, month and season. Studies conducted in Bangladesh for determination of effective rainfall since 1970s indicate that about 70 to 95 percent of total rainfall is effective during Aman ((Second Kharif) season. Effective rainfall in these studies was determined by using 10 to 15 cm levee heights and semi-empirical method suggested by Dastane with 3-day grouping for loamy soils. Study conducted in a pump cum gravity irrigation system indicates that pump operation can be suspended for 40 to 45 days during rainy season without any yield reduction, which will reduce operation cost and will encourage and influence farmers in timely planting of rice (Aman). An understanding of the characteristics of rainfall in relation to crop growth stages and soil condition are required for successful crop planning and for maximum utilization of rainwater. The onset of monsoon determines planting time and subsequent distribution of rainfall influences growth and development of crop. Rainwater management strategies should be considered depending on need and suitability in the wet season. Rainwater harvesting for stabilizing T. Aman production should get top priority in Bangladesh. In plain land, it could be achieved by means of a suitable ditch constructed at one corner of a plot. In hilly and Barind areas, the ditch can be located at a suitable place of the catchments. Studies conducted with 5m x 5m x 2m trapezoidal ditch found to be appropriate for storing rainwater enough for one supplemental irrigation of about 6cm depth. It has also been observed that a ditch size of 5% (2m deep) of the rice plot is required to conserve enough rainwater for sustaining rice productivity in wet season in Bangladesh. Benefit-cost (B-C) ratio of ditch irrigations were calculated for five years during early 1980s and the highest B-C ratio of 6.8 were found for the study in 1983. Five years average B-C ratio of 2.4 indicates that permanent ditch is profitable even if there is drought once in every five year cycle. Fish cultivation in the ditch will help to increase benefit from the ditch, which will require cleaning once in every three years. Studies conducted in Bangladesh confirmed that well managed 15 cm high levees could help to conserve significant amount of rainwater (91%) which can be beneficially used to obtain a good T. Aman crop if there is short duration drought. Rain water and part of surface flow during later part of monsoon can be stored in lowlying area, canals and ponds for supplemental irrigation of rice crops. There are opportunities to use pond water for supplemental irrigation to stabilize yield of Aman crop and for dry season irrigation. Observations have also been made that with one ha of pond about 10 hectare lands can be brought under supplemental irrigation for rice. The same pond can also be used for irrigating about 10 hectare of dry season non-rice crops. Excavation of ponds and re-excavation of existing canals will increase storage capacity 476
for subsequent use of water for irrigating the second crop. New ponds and re-excavated canals can also be used for fish cultivation (personal communication with fisheries experts). Fish cultivation alone in the ponds and re-excavated canals will be cost effective. Rivers especially smaller rivers can be compartmentalized to series of seasonal ponds during November to May through appropriate water conservation structures like weirs and rubber dams. Community based fisheries management system can be introduced in the seasonal ponds following the Common Property Resource Management Procedure of the country. Fisheries experts confirmed that these seasonal ponds could be brought under profitable fish cultivation program through stakeholder participation and on an average, 0.5 to 1.0 ton fish can be harvested per hectare of water body. Moreover, water stored in the seasonal ponds/riverbeds will be a continuous source for groundwater recharge, which subsequently can be used for irrigation using deep and shallow tubewells without severe lowering of groundwater table. River water conservation will also contribute to afforestation program along the riverbanks, irrigation development using low lift pumps for the lands adjacent to the rivers and availability of drinking water and bathing place for cattle. Success of this approach in one river may be replicated in other area of the country, which will contribute to its overall development. The national development plan should be to maximize utilization of rainfall, surface and ground water through conjunctive use of these resources. The development strategy will be to increase production per unit of land, unit of water and unit of time. INTRODUCTION Bangladesh is blessed with excellent quality of ground and surface water for irrigation, which is in abundance for the year-round use. However, distribution pattern of surface water availability over the years makes a complex condition for its profitable use and causes flooding almost every year sometime during June to September. The country receives about 90% of the surface water resources during June to October through rainfall and river flows, most of which flows to the Bay of Bengal. With management alternatives, part of it can be retained in crop fields (especially rice), rivers, canals and low areas and can be effectively used for agricultural (crop and fish production) and nonagricultural purposes during the lean period, November to May. Through conjunctive use of ground and surface water, about 76% of the cultivable area can be irrigated (MPO 1991 and WARPO 2000), of which about 60% are presently under irrigation (MOA 2005). Out of the present irrigated area of 60%, about 90% is irrigated using deep tubewells (DTWs), shallow tubewells (STWs), manually operated and low lift pumps (LLPs) which are popularly known as minor irrigation in Bangladesh. Rainfall distribution pattern indicate that water requirement for most crops be met from 477 rainfall only during May to September, since monthly rainfall during these months on an average is more than 200 mm. Therefore, sustainable crop production can only be expected with rainfall only during these months and irrigation is essential during other eight months of the year. Water conservation and management strategy of Bangladesh should be based on water availability conditions and improvement potential of different regions of the country and integrated management of flood control, drainage and irrigation (FCDI) infrastructure. The country may be divided into four zones depending on water availability, land capability, subject to annual flooding and agricultural practices. These are; Northwest, Coastal area, Central Flood plain and Hilly area. The specific areas considered under different zones in this paper are; (i) Northwest which includes area under present Rajshahi division and greater Kushtia and Jessore districts, (ii) coastal area, (iii) central flood plain which includes most part of central flood plain and remaining area of coastal belt where saline water inundation is rare, and (iv) hilly area of Chittagong, Sylhet, Comilla and Chittagong Hill tract. Development options through integrated land and water resources of these zones and FCDI infrastructure are explored and implementation
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National Seminar on Rainwater Harve
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once subsoil water starts draining
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The plantation process starts with
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DOLASANE , SANGAMNER RANGE I, SANGA
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Table 1. Present land use of waters
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the determination of specification
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Hydrological Parameters (mm) 140 12
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Drainage Engineering, 129(3): 184-1
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March to July, 2004 in the field si
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mm in 4 lph drip followed by 755.25
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Table 3 : Seasonal water use (mm) i
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pinnata) Aquatic plants are represe
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the base of the trench to assist dr
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SUDS (Sustainable Drainage Systems)
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Figure 3 : Cascade model of constru
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H eff = H R - H aq - H f ……..
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• Layers of gravel/media laid hor
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1.3 % annually, and the total energ
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Figure 1a. Schematic diagram of sol
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Figure 5. Cross-section of partitio
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Fig. 1 (a) - (d) : Water Level Soun
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farms and industries hope to get ad
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Geology of Area The area is a part
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ground water recharge, which includ
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Table - 3 : Salient features of the
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eing 6.08, pH value of AB 3 and AB
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Table 2 : Tolerance limit for metal
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CASE STUDY The Salem Municipality i
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After analyzing the characteristic
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1. Ash Pond water recycling System
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Poly Electrolyte Dosing RAIN WATER
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Canteen Waste Garbo-drain Bar Scree
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SERVICE WATER FOR SPAYING COAL CRUS
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In coastal areas of Gujarat, the vi
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Water diversion Channel The work fo
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04. Natural Water harvesting at Sol
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Work Done Storage No. of Area No. o
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Conclusions The process of rainwate
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Page 101 and 102: and weathering also control the wat
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Page 105 and 106: Ground Water Conservation Technique
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Page 113 and 114: water, use of improved seed and bal
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Page 125 and 126: echarging , A study of world wide f
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Page 133 and 134: The opinion of the public for the q
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Page 145: National Seminar on Rainwater Harve
Page 149 and 150: years. These beels can also be conv
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Page 153 and 154: contribute to increased fish produc
Page 155 and 156: Figure 1 : Map of Bangladesh showin
Page 157 and 158: end uses and the intentional manage
Page 159 and 160: INTRODUCTION Indian water sector is
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Page 169 and 170: REPORTB OF WORLD COMMISION ON DAMS
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