It is believed that Climate change is no longer an issue but an undisputable reality for the distant future. Rainwater Harvesting & Permaculture. Design "a" as described here has a C:CA ratio of only 1.4:1, and does not require provision for overflow. Under such circumstances water may be increased and surface area may be required to convey for long distance. Contours are surveyed by a simple surveying instrument such as a water tube level or line level (see appendix). Polluted water is unsuitable for drinking, recreation, agriculture, and industry. By means of a tape measure, the tips of the bunds are now marked along the "straightened contour". The tips of the bunds are only 20 cm high, and excess runoff drains around them. Even when this is possible it is equally important to introduce an appropriate and acceptable range management programme to avoid over-grazing and subsequent degradation of the range. Reurge delivers r & d services for water harvesting sector. Semi-circular bunds for rangeland improvement and fodder production can be used under the following conditions: Rainfall: 200 - 750 mm: from arid to semi-arid areas. Design "b", with larger and wider spaced bunds, is more suitable for drier areas, and does not need such even topography. Differing availabilities of stones can lead to inequalities between neighbouring areas: not everyone can benefit in the same way. Contour ridges for crop production can be used under the following conditions: Soils: all soils which are suitable for agriculture. Improved construction and alignment along the contour makes the technique considerably more effective. selection The calculation of the C:CA ratio is not necessary as the catchment area and the extent of the cultivated land are predetermined. Soils: Must be at least 1.5 m and preferably 2 m deep to ensure adequate root development and water storage. In recent years the Government has tested a similar system for rehabilitation of rangeland where, within the bunds, grass and trees were planted. It is suitable for the relatively "wetter" semi-arid areas but requires low slopes and even terrain. Even wider spacing could be adopted, and the "missing" structures "filled in" afterwards. Crops are planted on both sides of the furrow. However, the terraced wadi system is used in more arid regions, across clearly defined watercourses (Gilbertson 1986; Reij 1988). A diversion ditch should be provided above the block of microcatchments if there is a risk of damage by runoff from upslope of the block. Also as sprayers are increasing in size it means that they take longer to fill. The situation is different if animals have access into the bunded area and are allowed to graze. First Online: 22 May 2014. Contour bunds for trees are mainly made by machine; costs of bund construction can be relatively low and implementation fast, especially where plots are large and even and the kind of mechanization well adapted. All these adversities can be effectively mitigated by the use of rainwater harvesting units. Four main groups of water harvesting techniques can generally be distinguished: micro- and macro-catchments, floodwater harvesting and storage reservoirs. However in practice this may not be practicable due to the amount of stone and labour involved. Larger cross sections may be required dependent on catchment characteristics. Due to the larger dimensions of the bunds there are only 4 structures required per hectare. The size of the farm pond should be decided by the quantum of water to be stored and nature of the soil strata. Point D is then established with level and tape at the same ground level as C, at a distance of 25 m from C to allow overlap with AB. Suggested Book:Topic-wise Solved Papers for IBPS/SBI Bank PO/Clerk Prelim & Main Exam (2010-18) Reasoning/Quantitative Aptitude/English/General Knowledge. Thus there must be planning for repair work where necessary and careful inspection after all runoff events. The two designs of semi-circular bunds considered here differ in the size of structure and in field layout. This will ensure that the bund tips are more resistant to erosion when excess water discharges around them. If the structure is clay wool in that case depth may be increased and surface area may be reduced to have minimum evaporation. As discussed in Chapter 4, C:CA ratios of up to 3:1 are generally recommended for water harvesting systems used for rangeland improvement and fodder -production. It is advisable to plant an extra seedling in the bottom of the pit for the eventuality of a very dry year. China's arid Gansu province supplies water to the homes of 2 million people using small, spherical sub-surface tanks to collect rainwater, and is increasingly using water harvesting in agriculture 9. Stone bunds in West Africa are often used for rehabilitation of | infertile and degraded land. Good soil is nothing without water! 5.5.3 Layout and construction It is recommended that the bund should not be less than 25 cm in height. The maximum length of a base bund is recommended to be 100 metres. if farm is located in rocky and porous part, it would difficult to use stored water for crop production. Rainwater is collected at the roof top of the houses which is then sent to the storage tank via slope pipes. All these things discussed above should be combined into a method of management called “watershed based farming system”. Topography: area within bunds should be even. When used by a farmer on his own land, the system does not create any conflicts of interest between the implementor and the beneficiary. Where available, a reversible plough is preferred because furrows can be ploughed consecutively in both directions. The cross-section of the bund changes over its length. Waste water from manufacturing or chemical processes in industries contribute to water pollution. Negarim microcatchments are neat and precise, and relatively easy to construct. Plate 7 Grass grown in semi-circular bund. As mentioned previously, there are examples of similar structures being used traditionally in Sudan -where they are often made by hand, without assistance from any agency and evidently perform well. "Limanim" (plural of Liman) may be constructed in series along a wadi bed. Soils: agricultural soils with good constructional properties i.e. Runoff coefficients increased over years due to a soil crust formed over the microcatchment surface. 5.2.5 Husbandry First is the method of application and second the stage of crop growth. The final result will be a block of diamond-shaped microcatchments, with a first row which is open at the upslope end. The ditch should be constructed before the contour ridges are built to prevent damage from early rains. This method is suitable for area where rainfall is scanty (< 500 mm) and even there is difficulty of maturing a single crop. If, on checking, there is an error greater than 0.5 m in any of these three dimensions, the setting out procedure should be repeated. Contour ridges are limited to areas with relatively high rainfall, as the amount of harvested runoff is comparatively small due to the small catchment area. A horizontal spacing of approximately 20 metres apart is recommended for slopes of up to 1%, and 15 metres apart for 1 - 2% slopes. Floating blocks of wax rubber and plastic floats are more effective in controlling the evaporation to the extent of 80 percent. Bund heights vary, but are in the order of 20 - 40 cm depending on the prevailing slope. As far as possible the pond should be located in the lower patches of the field to facilitate better storage and less seepage losses. 5.3.4 Maintenance When no machines are available, this should be done by foot or with a barrel filled with sand. … Rain Water Harvesting – Why, Benefits, Techniques & More April 12, 2017 April 25, 2019 Editor Water plays a significant role in our lives since it is a precious natural resource. Keywords: China, conservation tillage, conventional tillage, rain-fed agriculture, Tunisia, water harvesting, water saving Contents 1. asphalt bitumen and water proofing membranes like paraffin. 5.6.5 Husbandry The average slope of the field is determined by a simple surveying instrument such as a water level or a line level (see Appendix) to decide on the spacing of the bunds. The spacing between bunds ranges normally between 15 and 30 m depending largely on the amount of stone and labour available. In common with all water harvesting techniques which rely on external catchments, the C:CA ratio is based on seasonal rainfall reliability in a year of relatively low rainfall. At this point, the plants have a greater depth of top soil. Table 21. There was a deliberate policy to "over-design", as food-rewarded labour was not limiting and it was desired to make the structures as maintenance free as possible. Diversion ditches should be 1 - 1.5 metre wide and 50 cm deep, with a gradient of 0.25%. The earth beneath the bunds should be loosened to ensure a good mating with the bund. This procedure will be repeated until all bund alignments in the first row have been determined. can be used for lining the pond surfaces depending upon the easy availability and cost of the material. The uncultivated catchment area between the ridges should be kept free of vegetation to ensure that the optimum amount of runoff flows into the furrows. If a series of permeable rock dams is to be built, an appropriate vertical interval (VI) should be selected. This technique is well suited to small scale application on farmer's fields and, given an adequate supply of stones, can be implemented quickly and cheaply. Labour rates for earthworks: Larger structures (e.g. By 1987 about 150 trapezoidal bunds had been constructed for the production of quick maturing food crops including sorghum and cowpeas. This is an issue which has to be seriously considered during the planning phase. Manuring (as described above) is very important in fertility management. The main crop grown is bulrush millet. As the soils become heavier, the crops change to sorghum and maize. Where a diversion ditch is necessary, an additional 62.5 m3 for each 100 metre of length of ditch has to be added. The main limitation of permeable rock dams is that they are particularly site-specific, and require considerable quantities of loose stone as well as the provision of transport. Where permeable rock dams are constructed in wide, relatively flat valley floors, they are sometimes made straight across - in contrast to the usual design where the spreader bunds arch back from the centre to follow the contour. In subsequent seasons the risk of breaching is diminished, when the bunds have consolidated and been allowed to develop vegetation - which helps bind the soil together, and reduces direct rainfall damage to the structures. The "Liman" system, principally reported from Israel, is used on flood plains or in broad "wadi" beds. The improvements being introduced are large earth diversion embankments in the main or subsidiary channels, and then a series of spreading bunds or "terraces". However eared or rectangular ponds are more convenient for harvesting of runoff water. This can be done most simply with an Abney level, or with a line level, as described in the appendix. iii) Water harvesting in farm Ponds: – A portion of the excess runoff water after allowing maximum in situ moisture conservation is collected in farm ponds. Climate change is … Traditional forms of water harvesting, similar to trapezoidal bunds, are found in the clay plains of Eastern Sudan and also in Somalia. Here water should be stored in soil profile rather than in farm pond. The water no longer spreads and the land is parched and eroding. 130 hectares, in blocks of about 10 ha in size and surrounded by solar-powered electric fences, were implemented up to 1987. Damage is frequently caused if animals invade the plots. 71% of the world’s surface is covered in water. 5.4.5 Husbandry Transport of stone increases this figure considerably. A vast number of techniques allow flexibility and adaptability to site-specific situations to best fight water scarcity and make . The excavated soil is placed downslope. Sorghum can tolerate both these situations. This is particularly important in the arid and semi-arid regions of Africa and may help to explain the failure of so many projects that did not take into account the people's priorities. Slopes: below 2%, but with modified bund designs up to 5%. Conserving water the traditional way. Earth should be excavated from both sides to form the bunds, and in the shallow trenches formed, earth ties should be foreseen at frequent intervals to prevent scouring. In the case of application of water for crop production two considerations need to be borne in mind. A larger C:CA ratio for design "b" is possible but it should not exceed 5:1. Because of variations in the slope, the lines may come closer together, or diverge at some points. The findings were encouraging. Considerable variations are possible dependent on climatic, physical and socio-economic conditions. This alignment is ideally along the contour, or as close to the contour as possible. The first action after aligning the extension arms of the dam is to dig a trench at least 10 cm deep and 280 cm wide (according to the base width of the bund). Crops and fruit trees utilize the residual moisture. It is particularly important to pack the small stones well at the lower levels to increase the rate of siltation. Design "a" has bunds with radii of 6 metres, and design "b" has bunds with radii of 20 metres. However, as with all mechanization in areas with limited resources, there is a question mark about future sustainability. techniques except for lnter-row water harvesting technique are shown in Figure 4 with their recommended parameter ranges. Besides harvesting water for the trees, it simultaneously conserves soil. This process is continued down the field. If bunds are spaced at more than 2 metres, the ridge height must be increased. As the implementation of water spreading systems is a relatively large-scale exercise, consideration has to be given to community organization. Although semi-circular bunds are mostly used for growing grass, bushes or trees, the technique is also suitable for crop production. Soils: alluvial fans or floodplains with deep fertile soils. Repairs to the wing tips will frequently be needed when overflow has occurred. Water Harvesting Techniques ithA bR iin the Arab Region By Abdelaziz ZakiAbdelaziz Zaki UNESCO Cairo Office Water Resources in the Arab region The Arab world is facing one of the severest water scarcities in the world. KINGSTON, Jamaica – The Ministry of Agriculture and Fisheries on Wednesday handed over conditional ownership for water harvesting infrastructure to 12 water user (farming) groups in … The first step is to measure the slope of the land, in order to select the appropriate bunding system. In general the seepage losses in deep black soils are low. Overflow discharges around the tips of the wingwalls. The grass is also used for thatching. Sorghum in wadi (Red Sea Hills). Negarim microcatchments have been developed in Israel for the production of fruit trees, but even there the returns on investment are not always positive. This lip should be pitched with stones for extra resistance to erosion. Maintenance will be required for repair of damages to bunds, which may occur if storms are heavy soon after construction when the bunds are not yet fully consolidated. Surprisingly, this technique has never been used traditionally. Figure 17 Negarim microcatchments - field layout. 5.3.3 Layout and construction Second – Flowering 65 – 70 Days. This leads to another problem - to what extent is the cost of stone transport justified? The bund should be constructed in layers of 10-15 cm with each layer being compacted and wetted first if possible. It has often been experienced that people consider it mainly as a job opportunity and lose any interest in the scheme once the project (and the incentives!) The sideslopes are usually 3:1 or 2:1 (horizontal: vertical) on the downstream side, and 1:1 or 1:2 on the upstream side. Once the trees are planted, it is not possible to operate and cultivate with machines between the tree lines. There are three important stages involved in water harvesting. 5.7 Contour stone bunds In this context it is recommended that the bunds be supported by a further technique - that of planting pits or "zai". Permeable rock dams improve conditions for plant growth by spreading water, where moisture availability is a limiting factor. The key to a successful stone bund is to eliminate any large gaps between stones. Each microcatchment consists of a catchment area and an infiltration pit (cultivated area). It should be noted that where a diversion ditch is required (Design "a" only), 62.5 m3 for each 100 metres of length has to be added to the figures in column 6. Construction begins at the top of the field as in all water harvesting systems. The skill of construction is in the use of large stones (preferably of 30 cm diameter or more) for the casing of the wall. Figure 46. Thus the quantity of water actually utilized cannot be easily predicted from the catchment size. Contour bunds are not suitable for uneven or eroded land as overtopping of excess water with subsequent breakage may occur at low spots. For design "a", the tips of one structure are 12 metres apart (2 times the radius) and the distance to the next unit is 3 m. For design "b", the tips are 40 metres apart and the distance to the next structure is 10 m. The centre point between the tips of each semi-circular unit is marked. The difference is that with WH the farmer (or more usually, the agro-pastoralist) has no control over timing. Some mechanical measures to increase runoff        can be adopted such as land surface smoothening reducing surface depressions compacting the soil surface by rollers of spreading the clay blanket before rolling in sandy soils. The real contour should be smoothed to a gentle curve. As in the case of all cropping systems under water harvesting, an improved standard of general husbandry is important to make use of the extra water harvested. This is again a microcatchment technique. This section is based on the design and layout of trapezoidal bunds implemented in Turkana District in northern Kenya. Design "b" is recommended on slopes up to 2%. Topography: must be even - areas with rills or undulations should be avoided. Spacing of rock dams (Source: Berton 1989). Table 21 gives quantities of earthworks required for different layouts. Considerable labour may be required to collect, and sometimes break, stone. When a diversion ditch is required additional earthworks of 62.5 m3 per 100 m length of ditch will be needed. As explained in the construction details, it is important to incorporate a mixture of large and small stones. Can vary from 0.1 to 1 ha of water harvesting techniques for agriculture, rather than allowing it to run off or. Of 1-2 %, and spread the diverted flow used rangeland is usually about 0.9 apart! 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