Agricultural Drainage

Bulletin 871-98

Ohio

Wetland Reservoir Subirrigation Systems

Wetland Reservoir Subirrigation Systems link a wetland and water supply reservoir to a network of subirrigation/subsurface drainage pipes that can be used to irrigate crops through the root zone. Proper linkage and management of these components has the following benefits:

1. supplies water to the crop, eliminating drought stress, improving plant nutrient use, and sustaining yields;

2. collects and recycles runoff and drainage waters, reducing the amount of sediment and plant nutrients lost from the cropland to surface waters; and

3. increases wetland acres, vegetation, and wildlife habitat.

A properly designed system has the potential for zero-discharge to streams, with the option to release clean water at a later date, helping to reduce peak flows downstream.

During and after a rain, runoff and subsurface drainage waters flow into the wetland. A water control structure in the wetland is used to maintain a ponded water depth of one to two feet. Vegetation that grows in the water, on the bank, and in the adjacent habitat area helps filter out sediment and nutrients from the flow. Water that flows from the wetland is pumped to the water supply reservoir for storage. Water in the reservoir can then be pumped to the subirrigation/subsurface drainage system to irrigate crops during the growing season. Subirrigation improves crop yields because crops receive a steady supply of water throughout the growing season. From the field, water drains back into the wetland, and the cycle starts again.

Two components of a wetland reservoir subirrigation system: (1) a
wetland (top photo), and (2) a water-storage reservoir (bottom photo) at
the Defiance County demonstration site.