136 | Green Roads for Water
PHOTO 8.1
Borrow pit from high-speed railway track to be converted to storage reservoir and landscaped into a local lake, Gaomi, Shandong, China
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OPPORTUNITIES In planning new borrow pits or in converting decommissioned borrow pits into water storage, preference should be given to those pits that meet the following criteria: • The pit can be connected to a water source. • The pit is located in an area of water shortage. • The pit is close to domestic, livestock, or irrigation water users. Borrow pits may be used for water supply in three ways: • W ater retention. The borrow pit is used for direct storage of runoff water. In such cases the pit should have a relatively impermeable bed to prevent stored water from leaking away. • Infiltration ponds. In this case, the water that is collected infiltrates and feeds the shallow groundwater. Such borrow pits should have relatively permeable beds to facilitate groundwater recharge. They may even be supplied by excess water from nearby streams diverted or pumped into the converted borrow pit. (See box 8.1.) • Seepage ponds. Borrow pits can serve as seepage ponds in areas with high groundwater levels, such as the floodplains of major rivers (photo 8.2). In this case, the pits will fill constantly with groundwater seeping from adjacent areas and provide an almost permanent water source.
