Road side ponds can be important sources of water. They need to be planned carefully in terms of catchment (in proportion to storage capacity), soil characteristics (not too porous), lining, their capacity (serving the requirements), sediment interception and protection from diseases (such as measures to control malaria)
Road side farm ponds can represent a critical additional source of water in dry lands. They can also be used in wet areas for irrigation and livestock watering during dry spells
A recurrent application to harvest water is to direct the runoff that is guided by the road body and the road-drainage system into farm ponds. These ponds will store water for additional irrigation, livestock water, or domestic water use. They can sustain high-value agriculture (see Box 10.1) or be a lifetime support for livestock. Roadside ponds are common in many countries, but they are not widespread everywhere. In many areas they could be connected to roadside drainage cuts or miter drains. The objective of this chapter is to discuss the development of these ponds, the opportunities they provide, and the recommended practices.
Box 10.1 Growing grapes with road water in Bolivia
In the area immediately to the south of the city of Tarija, grape production is the main cash crop for the majority of the farming community, which mostly relies on reservoirs for irrigation water. However, water distribution does not meet the ever-growing demand. High erosion rates are also decreasing the dams’ overall capacity. Some farmers along roads are successfully experimenting with road-water harvesting. There are many forms of storing road water: one of the most common is the use of water-harvesting ponds (atajados).
An example is from the San Jacinto Dam. The piped water running along the road is distributed at long and irregular intervals. The atajados help to buffer water and redistribute it. The small farm ponds were built at first as night storage infrastructures with the intention of storing water during irrigation turns. This gave farmers the freedom to apply water to their fields at the most convenient times. With growing demand and dwindling water supply, the atajados assumed a dual role. While storing water from the piped water system, they also began to be recipients of road runoff to compensate for the intermittent water supply.
Farm ponds are dug-out structures with definite shape and size, and with proper inlets and outlets for collecting the surface runoff flowing from a small catchment or part of a catchment, including the water guided by road bodies. The water leading to farm ponds can come from the roadside drainage system or its culverts, or can be guided by road embankments. As shown in Box 10.1, the ponds can receive water from several sources.
Farm ponds are one of the most important rainwater harvesting structures. In general, water leaving an area without serving the needs of that area can be considered as a lost opportunity. It is useful to systematically develop farm water ponds along road sections to capture the concentrated runoff, rather than letting it play havoc with the areas surrounding the road and eventually also undermining the road bodies themselves. An important method to capture this road-guided runoff is the systematic development of farm ponds.
Farm ponds may be used for irrigation (full or supplementary) and livestock watering. Upon treatment they can be used for domestic applications. Ponds can also be used for recharging groundwater, catchment protection (i.e., soil erosion control), ecosystem/biodiversity conservation and rehabilitation, and recreation.
The primary application of farm ponds is in dry lands where they can represent a critical additional source of water. However, farm ponds are not only developed for dry areas but can also be used in wet areas for irrigation and livestock watering during dry spells.