In-field water harvesting is the practice of increasing water infiltration and moisture retention in the soil. The agricultural technique involves the collection of rainwater runoff from fields that is collected and stored for future needs. This water can be stored in infiltration pits and later used to water the same crops, other crops through an irrigation system (usually high value crops, including fruit trees), or used for domestic purposes. Factors like soil, water, and plant type influence the effectiveness and productivity of rainwater harvesting. This type of water harvesting is generally implemented in areas of very low rain (semi-arid) conditions. In-field water harvesting entails establishing micro-catchments at the farm scale, where sloped areas have been cleared or cropped to direct rainwater to the water storage area (a pit that has been dug to store/hold water). Utilising strip cropping to growing crops while providing a method for directing rain is sometime practiced. The soil type has a limiting factor in collecting in-field water due the infiltration rates. In-field water harvesting saves rainfall water that can be used over a longer period than during and immediately after a rainfall event, reduces the risks of crop failure due to no or limited rainfall, and increases rain water productivity.
To effectively In Field Water Harvesting techniques, the following steps should be carried out:
- Step 1: Land is cleared, berms are developed, and crops are planted in order to direct water to the infiltration point.
- Step 2: The catchment areas should be sloped no more than 5 % and the area should be cleared to promote catchment as much as possible.
- Step 3: The infiltration pit (where water is stored) should be dug at the lowest point of the catchment areas and line infiltration pits with plastic or concrete roofing to limit water loss, and can be used as a source of irrigation for fruit trees and other high value crops.
- Step 4: Paths can be built of soil to guide water to the infiltration pit.
- Step 5: Alley cropping, or strop cropping can be used, with areas between trees and crops dug deeper like a trough to direct water to the infiltration pit.
- Step 6: To access water from infiltration pits, farmers can introduce a pumping system and water can be distributed around the farm as necessary
- The Food and Agriculture Organisation (FAO), 1991. A Manual for the Design and Construction of Water Harvesting Schemes for Plant Production. Italy,Rome.
- CGIAR 2011. In-field rainwater harvesting: A climate-smart sustainable production practice. Montpellier, France.
Benefits
- Harvested water used in irrigation systems.
- In-field water harvesting saves rainfall water that can be used over a longer.
- Reduces the risks of crop failure due to no or limited rainfall.
- Increases rainwater productivity.
Drawbacks
- Major issues with a dug-out infiltration pit is evaporation and seepage. Evaporation can be combated by the addition of mulch to water and seepage can be prevented by including some kind of liner (plastic sheet, concrete, etc.). In addition, large plastic, steel or concrete container can be built or sunk below surface to prevent major seepage. Roofs can be built over infiltration pounds or built containers to limit the loss of water to evaporation.
