Definition and Categorization of Small-scale Water Infrastructure

Transcription

1 Definition and Categorization of Small-scale Water Infrastructure Aidan Senzanje, Timoth E Simalenga and Jabulani Jiyane Technical Brief No. 01 February 2012

2 ACKNOWLEDGEMENTS This study was funded by Consultative Group on International Agricultural Research (CGIAR) Challenge Program on Food and Water; the authors wish to appreciate this support. 2

3 TABLE OF CONTENTS 1 Background Introduction Small-scale water infrastructure defined and categorized Types of small-scale water infrastructure Small reservoirs Small weirs and coffer dams Sand dam Sub-surface sand dam Boreholes Tube well Shallow well Wind mills (wind pump) Small scale irrigation Irrigated or food security gardens Family drip kits Treadle pump Traditional ponds Rainwater harvesting (RWH) Soil and water conservation works (SWC) Summary References

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5 ACRONYMS ARC CA CPWF FAO IAE MUS SADC SPFS SWI RWH WRC Agricultural Research Council Conservation Agriculture Challenge Program on Water and Food Food and Agriculture Organisation ARC Institute for Agricultural Engineering Multiple Use Systems Southern African Development Community FAO Special Programme on Food Security Small-scale Water Infrastructure Rainwater Harvesting Water Research Commission 5

6 1 BACKGROUND The Challenge Program on Water and Food (CPWF) is a global research-fordevelopment program. Its unit of analysis is the river basin, and it operates in the Limpopo, Nile, and Volta Basins in Africa, and the Mekong, Ganges and Andean system of Basins. The CPWF Basin Development challenge in the Limpopo is: To improve integrated management of rainwater to improve smallholder productivity and livelihoods and reduce risk. From 2010 through 2013, the CPWF will facilitate five projects in the Limpopo basin, all of which will contribute to the intended impact. The five projects are:- Limpopo Project 1 (Targeting and scaling out), Limpopo Project 2 (Small water infrastructure), Limpopo Project 3 (Farm systems and risk management), Limpopo Project 4 (Water governance) and Limpopo Project 5 (Learning for innovation and adaptive management). Under Limpopo project 2 (L2), a study on the status and performance of small-scale water infrastructure in the Limpopo basin will be carried out. The study shall be achieved through carrying out a detailed participatory study on selected sites where dysfunctional SWIs exist. Rehabilitation guidelines which shall consider governance, institutional issues, technical, environmental compliance issues and multiple use systems (MUS) shall be produced. Additionally, the study shall explore alternative design approaches of new SWIs that will support multiple use systems (small-scale cash crop irrigation schemes, domestic use, livestock watering, aquaculture, rural industries, etc), improve livelihood of the rural community, improved food security and nutritional requirements for children and women. The study shall be carried out in four countries that share the Limpopo basin and which are: South Africa, Zimbabwe, Botswana and Mozambique. This publication addresses one of the L2 outputs in trying to define SWI. Contact Details Agricultural Research Council Institute for Agricultural Engineering 141 Cresswell Street, Silverton, Pretoria, Private Bax x 519, Silverton, 0127 Tel (012) , Fax (012) Website: 6

7 2 INTRODUCTION The Limpopo River Basin is situated in the east of southern Africa between about 20 and 26 S and 25 and 35 E, and covers an area of km 2. The basin is predominantly semi-arid, dry and hot. The majority of the basin receives less than 500 mm mean annual rainfall against an average annual evaporation that ranges from 1600 mm to 2600 mm. The Limpopo Basin is prone to frequent droughts and rainfall falls mainly during October and November, making agricultural production very risky (likely crop failure in 75 90% of years). Access to water for small-scale agricultural production is low due to unavailability of adequate water infrastructures (Ncube et al., 2010). This result in low yields, food insecurity and high poverty levels linked with a high unemployment rate for the rural population in the basin. Despite the enormous investments made thus far towards water infrastructure and small-scale irrigation schemes in South Africa and other countries in the Limpopo province, the performance of most of them has remained very poor (Bembridge, 2000). The adoption rates of RWH technologies are low and many people do not have the knowledge of different RWH systems, their implementation, maintenance and management. Therefore, the central problem is to seek for causes of such failure and rehabilitation requirements for such Small-Scale Water Infrastructure (SWI). Furthermore, alternative design and management options that will enhance productivity, adoption and environmental compatibility shall require exploration. Identifying, adapting, implementing, demonstrating, promoting and provide training of various RWH structures on the production areas shall be assessed. However, right from the start, it is imperative that SWI are defined and categorized so as to bring about a common understanding of what is being dealt with. The categorization allows for the standardization of solutions resulting from the analyses of causes of failure and dysfunctionality of such SWI. This short report seeks to offer a definition of SWI and their categorization. 3 SMALL-SCALE WATER INFRASTRUCTURE DEFINED AND CATEGORIZED The focus of this publication is on the definition of SWI. The definition for water infrastructure can be approached from two related perspectives which are scale or size and use. In the context of this project, by definition, water infrastructure means any physical (or technical) hardware that is available and used by rural farmers or communities in capturing, collecting, controlling, using, managing and disposing of water. Infrastructure forms a base on which farmers rely upon in handling or managing water in rural areas. The concept of small-scale comes from either size or use or indeed both. An example can be given here of what is termed small-scale irrigation and smallholder irrigation the former is taken to mean irrigation that is of a small-scale in terms of size, whereas that latter means it could be a large irrigation scheme but being farmed (or operated) by farmers with small land holdings therein. All over the world, there are smallholder irrigation schemes that measure tens and hundreds of thousands of hectares they are 7

8 by no means small in size, but are operated on the basis of small units (as compared to a similarly large scheme operated by a single entity, like a commercial company). Small-scale water infrastructure is therefore defined as any technical hardware that is used by farmers in the Limpopo basin in managing water resources for both domestic and agricultural use, and is operated on a small-scale as well as by smallholder farmers. This definition allows the current CPWF project to include all possible technologies that are available and used by smallholder farmers. Two examples will be given to illustrate the importance of this definition. A small reservoir (technical definition) in a typical communal area in a country like Zimbabwe will be considered as small-scale infrastructure, but a similarly sized reservoir on a commercial farm would not necessarily be considered as small-scale infrastructure. On the other hand, a center pivot irrigation system on a commercial farm is considered large scale technology, but if the same center pivot system was being used to irrigate several smallholder plots (under its span), then it would be appropriate to consider it as small-scale infrastructure. Typical SWI that is likely to be encountered in the Limpopo basin under CPWF L2 project include the following: a) domestic use Small reservoirs Small weirs and coffer dams Boreholes (equipped and not equipped) Tube wells (equipped and not equipped) Shallow wells Windmills Sand dams b) agricultural use (both protective and productive use, both crop and livestock) Small reservoirs Small weirs and coffer dams Boreholes (equipped and not equipped) Tube wells (equipped and not equipped) Shallow wells Windmills Sand dams (open and sub-surface) Small-scale irrigation schemes Irrigated or food security gardens Irrigation schemes operated in a smallholder context Rainwater harvesting infrastructure Soil and water conservation works Treadle pumps Buckets and cans used for irrigation 8

9 Family drip kits c) rural development use Rural water supplies (small scale) As the list above indicates, this is basically technical hardware that is used in water management for both domestic and agricultural use, and to a limited extent for rural development. 4 TYPES OF SMALL-SCALE WATER INFRASTRUCTURE A brief description of each of the above is given in the following sections. 4.1 Small reservoirs Technically these are reservoirs with a dam height that is 8 m and an impounded volume of 1 million m 3. The definition varies slightly in the different countries in the Limpopo basin with the above definition applying to Zimbabwe whereas in South Africa, a small earth should have a dam wall with the height between 5 m and 12 m (ARC, 2004). The important point to remember is that the reservoir(s) must be put to use by smallholder farmers or be used on a small-scale. Generally reservoirs impound the total flow of a river and water releases are only possible through the spillways designed for that purpose. In most countries in the basin, one needs to register small reservoirs to the appropriate regulatory authority. In dry areas, small reservoirs are truly multiple use infrastructure whose uses include; irrigation, domestic, livestock watering, fishing, brick making, collection of reeds, wildlife, and recreation (Senzanje, et al 2008) Figure 1: Small reservoir in Insiza district, Limpopo basin, Zimbabwe 9

10 4.2 Small weirs and coffer dams A weir is basically a low level wall (normally concrete) that is put across a river so as to create temporary water storage or impoundment to facilitate pumping, water diversion, or other use, such as livestock watering. With a weir (coffer dam), river flow continues to take place over the weir wall. These are common water storage structures in all the four Limpopo basin countries. Figure 2: Weir dam on a river (Source: Internet) 4.3 Sand dam A sand dam is a reinforced wall of concrete (or impermeable material like clay) built up to 5 m high across a seasonal sand river. When it rains the dam captures soil laden water behind it the sand in the water sinks to the bottom, whilst the silt remains suspended in the water. With time, the dam fills up with sediments and, depending on the sediments, up to 40% of the sand volume is water filled. Sand dams can provide low cost clean water for various uses including domestic, livestock watering and agricultural use. Figure 3: Sand dam on an ephemeral stream (Source: Internet) 10

11 4.4 Sub-surface sand dam This is a sand dam that is completely covered by sediments or sand and water is harvested from the sand. In some cases, sub-surface water harvesting takes place in silted riverbeds were there is not even a reinforced wall or such a structure. Substantial water yields can be harvested from sub-surface dams on large river systems. On the Limpopo River in Zimbabwe there is extensive fruit irrigation taking place based on subsurface water harvested. Figure 4: Multiple use subsurface sand dam (Source: Internet) 4.5 Boreholes This a hole that is drilled or driven into the ground to tap groundwater for multiple uses such as domestic, irrigation and livestock watering. Typically a borehole needs to be equipped in order for it to be useable. Equipping a borehole entails casing the sides of the hole, screening the lower part of the hole, installing a pump and then preparing the ground surface with concrete to minimise contamination of the water. Boreholes are very common in the Limpopo basin as water sources for both domestic and livestock watering. The depth of boreholes varies significantly depending on the depth to groundwater and the geology of the area. Depths can be in excess of 100 m. 11

12 Figure 5: Equipped borehole in Lambani, Vhembe District, Limpopo basin, South Africa (Source: Jiyane J.) 4.6 Tube well This is term that is more common in Asia than Africa and refers basically to a borehole that has a hole that is slightly larger in diameter (up to 300 mm) compared to a standard borehole. Equipping a tube well is the same as equipping a borehole. Figure 6: Tube well (Source: Internet) 12

13 4.7 Shallow well This is normally a hand dug well that can be several meters wide at the surface and a few meters deep. Shallow wells are quite common in the Limpopo basin and tend to be used mainly during the rainy season for domestic water supply and limited gardening, and then dry-off during winter. Shallow wells tap shallow ground water, and because they are open they run the risk of water contamination. Figure 7: Shallow well used for domestic water and garden irrigation in Mabalane, Limpopo basin, Mozambique (Source: Jiyane J) 4.8 Wind mills (wind pump) This is infrastructure that makes use of wind energy to provide energy for pumping underground water. In the past windmills used to be huge cumbersome structures but modern designs are now much more compact and efficient at converting wind energy to pumping energy. Windmills are very common in the dry parts of the Limpopo basin and have been used for years for livestock watering in Zimbabwe and South Africa by commercial farmers. 13

14 Figure 8: Wind mill for groundwater pumping in the South Africa Karoo (Source: Internet) 4.9 Small scale irrigation These are irrigation methods and practices that are adaptable to small-scale farmers and include the following the smallholder irrigation schemes family drip kits and treadle pumps. Small-scale irrigation is widespread in Sub-Saharan Africa and the Limpopo basin. Prior to the 1980s, small-scale irrigation was focused mainly on protective agriculture (ensuring food security), but since the 1990s the focus has shifted to include productive agriculture (both food and cash generation for improved livelihoods). Despite spirited efforts by governments and international agencies like the World Bank and FAO, the performance of small-scale irrigation has not been up to expectations most of the small-scale irrigation schemes are operating sub-optimally and failing to deliver on the expected benefits. 14

15 Figure 9: Small-scale irrigation in Siwaze, Limpopo basin, Zimbabwe 4.10 Irrigated or food security gardens These are fairly small irrigated plots (measured in mere m 2 ) near watering points or the homestead and used mainly for production of vegetables for home consumption. Watering is usually manually by bucket or watering can. In more recent times advanced technology such as family drip kits coupled to treadle pumps have been introduced to try and improve water productivity in these irrigated gardens. 15

16 Figure 10: Irrigated garden near Siwaze, Limpopo basin, Zimbabwe 4.11 Family drip kits These are small-scale drip kits specifically designed and produced to be used at a family level for household food production, with an emphasis on nutrition foods production. These typically consist of a few drip lines on a manifold connected to a bucket or drum that supplies water. A lot of these were supplied to many communities in Southern Africa under the FAO Special Programme on Food Security (SPFS). The uptake of these by rural communities in dry parts of the region has been a mixed bag, the main problem being access to water. Figure 11: Family drip kits used for vegetable production 16

17 4.12 Treadle pump This is a human-powered pump designed to lift water from a depth of 7 m (depending on location). Treadle pumps originated from Bangladesh and have been adapted and adopted for many places. In the SADC region, the treadle pump has had a mixed story successful in countries like Malawi and not very successful in places like Zimbabwe. The main factor leading to success or failure seems to have been to do with depth to pumping water table. In the flood plains of Malawi, the water levels are quite shallow thus enabling the use of treadle pumps whereas in Zimbabwe water tables tend to be deeper making it near impossible to pump any water Traditional ponds For several years now, the rural African communities have been collecting water into man-made or traditional ponds close to their homesteads. These were dug mainly down the slope from the homesteads, and were used to store water for crop watering as well as livestock consumption. The ponds were aimed at bringing and concentrating water resources around homesteads and occasionally on agricultural land. The construction was uncomplicated, though it involved sustained intensive labour. The ponds were hand dug pits mainly, constructed with picks, hoes and shovels. They varied in both depth and diameter though on average was about 2 metres deep and some five meters in diameter. On occasions some households erected stone-work to support the walls and the bottom base against erosion during excessive inflow. The pond constructed with stone cover, along the walls as well as on the base, could store the collected water for a long period since very little was lost through infiltration. Nevertheless, because of its muddy state the ponds stored water was not recommended for human consumption. None the less, the stored water was still collected with hand containers such as clay buckets and used for supplementary irrigation to crops close to the homestead. On grazing land, livestock were also allowed to drink freely from the uncovered ponds (Dennison and Wotshela, 2009). Figure 12. Traditional ponds (Dennison and Wotshela, 2009) 17

18 Figure 13: A treadle pump 4.14 Rainwater harvesting (RWH) This is the capturing, accumulation, storing and use of rainwater. RWH is a much wider field of study and in reality ranges from small reservoirs to in-field water harvesting and rooftop water collection. RWH enables the capturing of water for domestic, livestock and crop production uses. RWH systems range from basic structures to more complex industrial arrangement. For the purposes of this project, RWH will be limited to domestic, livestock and agricultural use. Figure 14: Infield rainwater harvesting techniques (FAO, 2009) 18

19 4.15 Soil and water conservation works (SWC) These are any works (infrastructure) that are designed and constructed in agricultural land with the sole purpose of conserving soil and water. Again, soil and water conservation works is part of the general RWH, except that in the past SWC tended to be associated with engineering or technical aspects only of soil and water conservation on the land. The definition today also includes practices such as conservation agriculture (CA). Figure 15. Soil water conservation structures using potholes (Simalenga, 2010) Figure 16. Soil and water conservation structures using tie ridges (Simalenga, 2010) 19

20 Figure 17 and 18. Infield runoff and rainwater harvesting (Botha et al., 2003) 5 SUMMARY SWI is defined as any physical hardware that is used by farmers to manage water in the Limpopo basin for both domestic and agricultural use and is operated on a smallscale. Typical SWI to be found in the Limpopo basin includes; small reservoirs, small weirs, boreholes, tube wells, shallow wells, windmills, sand dams (open and subsurface), small-scale irrigation schemes, irrigated gardens, irrigation schemes operated in a smallholder context, rainwater harvesting infrastructure, soil and water conservation works, treadle pumps, buckets and cans used for irrigation. Such a wide diversity of SWI implies there are going to be a wide variety of reasons why SWI fails or is dysfunctional in the Limpopo basin, and consequently the requirements for its sustainable rehabilitation and modernisation are equally diverse and demanding. 6 REFERENCES ARC Design Manual. Silverton, Pretoria, South Africa Bembridge, TJ Guidelines for rehabilitation of small-scale farmer irrigation schemes in South Africa, WRC Report No. 891/1/00, South Africa. Bongani Ncube, Emmanuel Manzungu, David Love, Manuel Magombeyi, Bekithemba Gumbo, Keretia Lupankwa The Challenge of Integrated Water Resource Management for Improved Rural Livelihoods: Managing Risk, Mitigating Drought and Improving Water Productivity in the Water Scarce Limpopo Basin. Project Number 17, CPWF Phase I Project Report Botha, J.J., Anderson, J.J., Groenewald, D.C., Nhlabatsi, N.N., Zere, T.B., Mdibe, N., and Baiphethi, M.N On-Farm application of in-field rainwater harvesting techniques on small plots in the central region of South Africa. Report No. TT 314/07, Water Research Commission, Pretoria. FAO (Food and Agriculture Organization of the United Nations) Scaling up conservation agriculture in Africa: Strategy and approaches. Adis Ababa, Ethiopia. Senzanje, A., E Boele, S. Rusere Multiple use of water and water productivity 20

21 of communal small dams in the Limpopo Basin, Zimbabwe. Irrigation and Drainage Systems (2008) Vol22: