Water harvesting techniques for arid and semi arid regions

Arid regions are known for prolong drought periods, leading to water scarcity. Some water harvesting techniques can be applied to ensure water availability during drought periods.

1. Water harvesting techniques for arid and semi arid regions

2. Introduction: Water is one of the crucial natural endowments for survival of human beings in particular and for living things in general. Water harvesting is an exercise that has been implemented by several countries as a various types of water harvesting technologies available in different semi-arid and arid areas; to show feasible means of water management techniques. It has been experienced that there is an increasing need of the cautious use of the limited fresh water resources, and sustaining and recharging the groundwater in different parts of the world from time to time

3. Introduction: For these reasons, different measures have been taken to manage water resources in many semi-arid and arid parts of the world. Implementation of varied water harvesting techniques, storage and water recharging mechanisms are among the measures taken by actors working in water sector.

4. Flood Water Harvesing Tanzeela Iqbal

5. Techniques under floodwater harvesting: Some major technologies classified under floodwater harvesting are as follows: Spate irrigation Floodwater and runoff farming Harvesting of water from concentrated runoff for irrigation purposes Development of degraded dry river valley by water-spreading weirs Jessour

6. Spate irrigation: It is sidetracking periodic floods of short interval from short-lived streams to water cascades of flattened and embanked grounds in the surrounding areas by applying old-fashioned water diversion and dissemination technique. This technique is applied in the case of Eritrea.

7. Floodwater and runoff farming: This technique is accumulation of water which is practiced in Ethiopia. It aims to collect flood water and overflow from short-lived streams, roadsides and hillsides via impermanent rock and soil ridges for rising crops, vegetables, and fruit trees.

8. concentrated runoff for irrigation purposes: This water collecting technique is practiced in the case of Spain. It is done by building bunds using slight stone to change the direction of the flood water on the way to almond plantations and/or cereals production sites from recurrent watercourses.

9. Development of degraded dry river valley by water-spreading weirs: Distribution of floodwater to nearby farming site by designing structures that can cover the whole part of basin. The purpose of the weirs is to disseminate the overflow water that come from valley floor and to enable the soil infiltrate ample water. This technique is not used for storing water for long time rather to distribute the overflow mainly to farming sites.

10. Tabia : Tabia sand ditch is a technique of water harvesting made in the gentle slope and bottom hill areas. It is usually prepared either in the bottom of foothills, inside or nearby to across the riverbeds at the foot portion of the watershed, in a place where a slope is not going beyond 3 percent and top soil is reasonably deep.

11. Jessour : Jessour water harvesting technique is also applied in Tunisia which is an ancient overflow water harvesting technique mainly practiced in the semi-arid and arid highlands with slant plots. In this case a dyke which is made of earth is used as a block to prevent back sedments and overflow water, and then plants are grown on this part.

12. Macro-Catchment water harvesting Usama Yaqoob

13. Techniques under Macro-Catchment Harvesting. T he macro-catchment water harvesting group has been classified into following: S mall earth dams. S unken streambed structure R echarge well S and dams.

14. Small Earth Dams In many tropical, subtropical and Mediterranean climates, dry season agriculture and the pre-rainy season establishment of food and cash crops cannot be undertaken without large quantities of water. To rely upon streamflow at a time when temperatures and evaporation are often at a peak can be unrealistic and risky. It may become essential for a dam to be constructed on a river or stream to allow for off-season storage of vital water supplies Thin units of gorge are constructed using small earth barriers or dams to store runoff created from upriver catchment areas.

15. Small Earth Dams P rincipal uses include Irrigation Stock and domestic water purposes, Drainage sumps Groundwater recharge Conservation storage. Fish farming Zambia is among good example of the cases where this technique is applied.

16. Sunken Steam-bed Structure It maximizes water volume using thin fountains for additional irrigation by diggings in streambed to deliver provisional storage of overspill. This technique is implemented in India.

17. Recharge well It is a drip irrigation technique intended for lowest use of labor and water for the best irrigation of crops and vegetables in semi-arid and arid areas. Injection or recharge shafts are essential to properly flow water towards deep aquifer of land. Injection shafts are appropriate basically in zones where there is thick impermeable or slowly penetrable layer between the surface of topsoil and the aquifer. This type of technique of water harvesting is practiced in Tunisia .

18. Sand Dams It is a stepping-stone brick wall across a periodic sandy river bottom that captures soil and rainwater rolling down to the drainage area. It is a simple, cheap and easy to maintain, reproducible water harvesting technique. The harvested water is clean and can be used as: D omestic water for households’ consumption. Irrigation purpose in dry and semi-dry areas. It is applied in Kenya.

19. Micro-Catchment Water Harvesting Ubaid Abdul Khaliq

20. Vallerani System A distinctive plough fixed with a tractor that mechanically builds catchments for harvesting water. The VS uses the  Delfino plow  invented and patented by Dr. Venanzio Vallerani and manufactured by Nardi . The plow creates a system of micro-basins and underground bags which collect rainwater, over flow. The water is saved from runoff by the tractor-pulled plough against evaporation and the water exists to plant roots and groundwater

21. Land Prior Processing

22. Ploughing with delfino

23. A erial view of the processe land.

24. Seeds of native plants are colected and planted

25. Rainwater collected in the micro-basins

26. Results during the rainy season and a few months after

27. Planting Pits The method involves digging holes into the ground, preferablly during dry times. P lants are sown later on at the start of the rainy season in these pits and hole. The pits measure between 10 and 20 cm in depth and 20 and 40 cm in diameter  Pits are s paced approximately 1 m apart from each other. To optimize the situation on the fields, planting pits are often used in combination with contour stone bunds. 

28. Purpose Ensure an efficient collection and concentration of rainfall runoff and nutrients. Bring degraded land back into cultivation.

29. Technical Diagram

30. Pitting visual

31. Stone lines and Counter Bundles Contour stone bunds (35-40 cm wide and approx. 25 cm high) are embedded 5 to 15 cm in the ground.  These countour stone budes made of a mixture of small and largestones . They are constructed along the natural contour of the land in series behind each other,. Spaced 20-50 cm depending on the slope of terrain Th e bunds form a barrier that slows down runoff. This effect is increased when small stones are placed at the upslope and larger stones on the downslope side of the contour bund. 

32. Purpose Re duces erosion. I ncreases water infiltration into the underground. Tr apping waterborne rich sediment particles, which results in an improved soil fertility.

33. Stone Lines

34. Furrow-enhanced runoff harvesting for olives: Runoff harvesting through annually constructed V-shaped microcatchments , enhanced by downslope ploughing. The V-shape earthen bunds (reinforced with some stones) are constructed manually, by hoe, around each tree.  The furrows then divert runoff systematically to the microcatchments where it concentrates in basins around the trees. Each tree is effectively served by a catchment area of 60 m2. The bunds need to be rebuilt every year. If the structures are damaged after a heavy storm, they need to be repaired

35. Purpose of the technology Degradation protect a watershed P rotect a watershed/ downstream areas – in combination with other Technologies

36. Advantages Sa ves irrigation water during the dry season En hances soil moisture storage Stimulates tree growth Te chnology is easy and cheap to maintain

37. Furrow-enhanced runoff harvesting:

38. Fanya juu It comprises embankments which are built by plowing waterways and layering the topsoil to avoid drainage of loam and water. The name  Fanya juu  means “throw it upwards” in Kiswahili it consists of terrace bunds and ditches along the contour.  Fanya juu  is suitable for slopes of 5-20%

39. Purpose Prevent water and soil loss  In semi-arid areas is to harvest and conserve rainfall in sub-humid zones, contour bunds are constructed to discharge excess runoff .

40. Fanya-juu