Global Theme on Agroecosystems
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Global Theme on Agroecosystems
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Towards sustainable watershed development and management: the case of participatory design and construction of a communal drain system
In the past, improved watershed management was generally synonymous to achieving a particular, often single technical objective, e.g. improved forestry, better soil conservation, or the introduction of water harvesting. These projects were initiated and executed with little or no real involvement of farmers. The new approach regarded watershed development and management in its entire complexity, where inter-related factors and their interactions are considered with the main objective of poverty alleviation and food security of watershed communities (Sharma and Krosschel, 1998). With the new emphasis on poverty alleviation and food security through appropriate natural resources management both people and natural resources become the primary focus of integrated watershed management (Pathak and Klaij, 2000). Over the past six years, the Joint Vertisol Project (JVP), a consortium of research institutions, working with extension services and smallholder farmers, developed technologies for raising the productivity of Vertisols of the Ethiopian highlands. Three elements particularly important for Ethiopian highland conditions were adapted from an improved Vertisol technology cropping system developed by ICRISAT for India (El-Swaify et al., 1985). Central element to the success of this technology is BBF, an effective soil and water conservation and surface drainage system. We address the case of the participatory design and construction of a main drain system in the Joint Vertisol Project agricultural micro-watershed in Ginchi. Through the combination of abundant main rainy season rainfall, cool temperatures and the intrinsically low hydraulic conductivity of Vertisols, severe surface water logging and runoff occur from July until the end of the rains by mid September. Poor field drainage is the norm in this critical period resulting in production loss and deterioration of the resource base by water erosion. Indeed, farmers of the watershed considered rainy season water logging a primary constraint to increased agricultural production and farmers accorded highest priority for improved drainage. During watershed walks and discussions with farmers, Ministry of Agriculture, and other stakeholders' farmers decided on the design and construction of a main drainage system and a cutoff drain. Agricultural gravity drainage systems Surface drainage systems are applied when water logging occurs at the soil surface, which is the case in the Ginchi, and other Vertisols areas in the Highlands. It is primarily intended to reduce ponding and prevent prolonged saturation of the upper soil profile, by accelerating flow to an outlet without causing undue siltation or soil erosion. Therefore, on the one hand we are concerned with removing agricultural constraints (improve field conditions for crop growth), and on the other hand with conserving the resource base applying engineering principles to ensure non-erosive water flow through channels and waterways. These waterways tend to follow the maximum slope. Slopes are moderate in the Ginchi watershed; hence, grassed waterways are appropriate. For slopes less than 5%, allowable velocities for erosion resistant soil covered by dense grass is 2 m s -1 . In our design of the waterway we adopted an allowable flow velocity of 1.7 m s -1 , a roughness coefficient of the Manning formula of n=0.04, and a parabolic cross section shape.
Peak runoff rates determine the required cross sections of the main drain and culverts. The magnitude of the peak runoff relates to the frequency of occurrence; very high rates occur less frequently. To accommodate a very high peak runoff rate can be expensive, as channel cross section have to be larger. The challenge is therefore to compromise between expensive designs that work most of the time, and much less expensive ones that will fail occasionally. For main drain designs, return periods of 5 to 25 years are usually considered (Boonstra, 1994). At the time of the waterway construction only one season of runoff measurements in the micro-watershed had passed. We therefore decided on a design runoff rate of 0.05 m3 ha -1 s -1 somewhat lower than the 0.06 m3 ha -1 s -1 based on Cooks model (Soil Conservation Service, 1972) when using a 10-year return period for rainfall. Presently we have eight years of runoff data available, and it seems that the then adopted design peak runoff rate is realistic for a 5 year return period (Fig. 1). The existing gully system was largely inadequate to accommodate the adopted design peak runoff rate, as was already apparent from severe gully head erosion in the watershed. Farmer view of main drain design aspects Following extensive watershed transect walks and discussion meetings farmers expressed their interest in improving external drainage in their watershed. However, they were unwilling to do the necessary reshaping and increasing the size of the existing gullies running through their fields because it would take out part of their individual productive land. In a series of meetings held in the spring of 1995 farmers, Ministry of Agriculture extension staff, and project staff discussed possible alternatives. Eventually, farmers agreed to project a main drain (grassed waterway) on the 2 to 10 m wide communal grassed pathways that cross the watershed. This was an excellent alternative because firstly it allowed the projected waterway to largely follow the maximum slope of the natural gully system. Secondly, the projected waterway would greatly improve the overall drainage situation because not only would the new waterway increase the existing gully system by 0.85 km, most of the runoff would bypass these gullies. Therefore, the size of the gullies would be amply sufficient to serve as stable field drains. In addition, farmers agreed to construct a cutoff drain, up slope of the 45 ha sub-watershed with the aim to divert water from an up slope 15 ha into a large gully, thus stopping it from running through the micro-watershed. Farmers were however reluctant to accept the much wider and deeper drains than they were used to, necessary to expel runoff safely. Because the runoff contributing area steadily increases from the top of the watershed to its outlet, the runoff flow through the waterway correspondingly increases. We envisaged 6 successive waterway sections to cope with the expected runoff volumes. Waterway section parameters are given in Table 1. In the new situation a total of 89 fields would be bordering and draining directly into the man drain, while the 29 fields draining directly into the gullies that served as secondary drains. Farmers could add a few more secondary drains linking more fields to the main drain at a later stage. This allowed for a flexible modular approach enabling farmers to invest time and effort at their convenience to improve drainage of fields not yet properly connected. Implementation of the new main drain required considerable earth moving (Table 1.)
Table 1. Adopted parabolic section dimensions and characteristics of a main drain grassed waterway, based on a design discharge of 0.05 m 3 s -1 ha -1 , a Manning roughness of n=0.04, and a maximum flow velocity of 1.7 m .s -1 .
The project emphasized that sustainability and success of community action for such common work as a drain would depend a great deal on the capacity of the local people to organize themselves rather than depend on the external agencies. That is why, shortcut methods and use of force or compulsion, directly or indirectly, should be avoided even when a slightly longer time is required to organize people and make impact. So in order to ensure replicability of such effort, the project staff facilitated discussion meetings and raised issues in addition to those raised by the farmers and encouraged them to take decisions on the points mentioned below. A number of meetings were required to agree on those procedural matters:
Work started in May 1995 just ahead of the main rains. Forty-one farmers who had land in the watershed worked together voluntarily to construct the drain. In total 33 out of 53 sampled households participated thereby moving an estimated 500 m 3 of earth requiring 173 person days. Obviously, participation was influenced by individual benefits farmers expected to gain from the communal waterway. Determinants of participation Tests have shown that either of the two definitions of participation was appropriate for explaining determining factors, so the broader definition was adopted (Gaspart et al., 1998) . The best fit estimated Tobit equation is as follows:
It is evident from the results that all the coefficients are of the expected sign. However, four variables are highly statistically significant: LAND (at 1.6% level of significance); PROX (at 0.11percentage); CAPL (at 0.14%); and LEAD (at close to 0.00%). In particular, the larger the land area of a farmer in the watershed where a drain was constructed, greater was the willingness to participate and contribute because of the possibility of deriving larger gains from the use of the new technology. Similarly, land area as such in the watershed may not be adequate if most of the fields are not located near the drain to benefit from it. We found that nearer the plot to the proposed drain, greater was the probability and degree of participation. Farmers with a larger capital (in this case draught animal, the principal form of capital in the watershed) per family work force were more likely to participate and contribute more because of the potential for deriving benefits by using animals and the BBM. Farmers in any leadership position in the Peasant Association (member, chairman) were more inclined to participate and contribute more to the construction. It is noteworthy that members of the executive committee of the local Peasant Association have contributed an average of 22 hours, compared with 12 hours for all participating households and with 7.5 hours for all sample households (whether they have participated or not). The reason may be that members or chairman of a Peasant Association may want to maintain their leadership and role model status in the community by participation and demonstration. Although access to outside income was not a statistically significant factor, its negative sign indicates that families with access to non-farm income (because of higher education of children or because of business), particularly when such income is high in relation to farm income, may show less interest in participating and contributing to common drain construction. This seems logical as these farms, at least in the beginning may see secured non-farm income as more attractive than uncertain potential income from the drain and the BBM technology. In addition to this general pattern, we also encountered evidence of the usual 'free rider' and 'prisoner's dilemma' problems in collective action. Some farmers having plot(s) close to the main drain or within the sub-watershed did not participate, though they adopted the BBM technology during the ensuing crop season and derived benefit from improved drainage. Others in similar situations contributed knowing that non-participant would also benefit. On the other hand, some farmers not having any plot within the sub-watershed or having a plot but not planting improved wheat in the ensuing season contributed labor perhaps because they expected benefit in the future. The earthwork was started from the bottom end of the sub-watershed and fewer farmers participated in the beginning but as the work progressed and it became evident that the drain would be constructed, more farmers joined in. By the time the work reached the end of the sub-watershed, more farmers started coming and requesting to expand the drain length to cover more land. This was, however, not possible in that year. There may be other important factors in specific locations, which may positively or negatively influence participation. It is important to identify such factors in consultation with the community and take appropriate approach to motivate and induce maximum voluntary participation by the farmers who are likely to benefit from such enterprise. Individual farmer motivation to participate and make voluntary contribution depend largely on the potential personal gains that the farmer can expect from a common drain system. It may be necessary to identify important motivating factors in each location and develop approach to participation accordingly. Farmers cultivating the watershed appreciated the drainage improvement brought about by their communal drain. In the spring of 2000, farmers cultivating an area close to the micro-watershed solicited technical information before they started their own, much more limited in scope, communal drain development. An important question is, can we expect resource poor farmers, whose land tenure is not secure to invest in watershed-based communal drainage and soil conservation measures? Benefits of this "structural" intervention accrue over years to individual farmers, but benefits in terms of reduced land degradation and reduced sediment downstream may be valuable to the society as a whole. The Indian Government recognizes the contribution of farming communities to the welfare of the society, spending on average US$ 100, - per hectare for participatory watershed development. The watershed is typical of the region, its altitude is 2200 m asl, annual rainfall is 1139 mm, annual reference evapotranspiration is 1296 mm, and mean temperature is 16.3 °C. Around Ginchi, the mean main rainy season rainfall, from July through September, is 602 mm; the mean potential evapotranspiration is a low 263 mm. A topographical survey provided data on terrain elevations, field boundaries and ownership, gullies and gully boundaries, pathways, trees, and settlements of the Ginchi micro-watershed. The data were geo-referenced. The 45 ha micro-watershed is cultivated by 64 farmers, of whom 6 women farmers, using 152 fields having an average size of 0.3 ha. The upper part of the oblong (1000 x 450 m) watershed is convex with slopes ranging from 2.3-3%, a steeper middle part with slopes up to 4%, and a concave lower part with slopes as low as 1.6%. The major drainage axis is 1100 m long, covering an elevation difference of 23.4 m. Pathways that are grassed had a total length of 4.6 km, covering 1.4 ha. About 2.1 km of field gullies comprised an imperfect surface drain system in the 45 ha sub- watershed. Imperfect because many gullies were not stable, and were not or poorly connected. In addition, only 29 fields out of the total of 152, or in area 11 out of 45 ha, bordered hence directly drained into this badly connected gully system. Ginchi is a typical teff growing area, between 1994 and 1998 farmers cultivated teff annually on over 50% of the watershed area. Farmers, who cultivated improved wheat on 2-20% of the micro-watershed area, depending on the year, adopted the Improved Vertisol wheat technology. Important N-fixing legumes such as chickpea and roughpea were grown on 7 to 10% of the total area. Farmers using the improved Vertisol wheat technology recognized improper drainage being a constraint to crop production.
References: Boonstra J . 1994. Estimating peak runoff rates. In ILRI Publication 16. Second Edition (Completely revised). Drainage Principles and Applications International Institute for Land Reclamation and Improvement, P.O. Box 45, 6700 AA Wageningen, The Netherlands, 1994 El-Swaify SA, Pathak P, Rego TJ and Singh S. (1985). Soil Management for Optimized Productivity Under Rainfed Conditions in the Semi-Arid Tropics. In: Advances in Soil Science, Volume 1, 1-64, (Ed B.A. Stewart). Springer-Verlag, New York Berlin Heidelberg Tokyo. Gaspart F, Jabbar M, Melard C and Platteau , Jean-Philippe. 1998. Participation in the construction of a local public good with indivisibilities: an application to watershed development in Ethiopia. Journal of African Economies, 7(2):157-184. ICID Committee on irrigation and drainage construction techniques. 1982. ICID Standard 109, Construction of surface drains. ICID Bulletin, 31, 1, pp. 47-57. Kampen J. (1982). An approach to improved productivity on deep Vertisols. Information Bulletin No. 11. Patancheru, A.P., India; International Crops Research Institute for the Semi-Arid Tropics. Pathak P and MC Klaij . An approach to sustainable watershed development and management. Paper submitted for the International Symposium. Sharma PN. and C Krosschel . 1998. Sustainable participatory watershed management. PWMTA-Farm Field Document No. 6. PWMTA Program, Katmandu Nepal. Pp 73-79. Soil Conservation Service, 1972. National engineering handbook, Section 4, Hydrology. Department of Agriculture, Washington, 762 pp.
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