Guest Post: Agricultural Drainage Wells
By Mike Bourland, IDALS-DSCWQ
Those in agriculture, especially north-central Iowa, recognize how important drainage is for improved row crop performance. In the early to mid-1900s, some farmers who needed to provide drainage for their fields installed Agricultural Drainage Wells (ADWs). ADWs are vertical wells that extend into fractured limestone to provide drainage for field tiles. These ADWs were placed in low-lying areas where there was no other practical and cost-efficient means of drainage. A typical ADW was designed to drain up to 100 acres.
Due to environmental concerns, the State of Iowa passed the Groundwater Protection Act in 1987. The law provided for registration of ADWs and also provided a source of funding for research and demonstration projects relating to ADWs and sinkholes. Research began in 1989 at the Drainage Research and Demonstration Project site located outside of Gilmore City in Pocahontas County and studied both closure and continued use of ADWs. Some of this research led to the development of the Iowa Conservation Reserve Enhancement Program (CREP), which includes construction of nitrate removal wetlands within tile-drained landscapes. Nitrate removal wetlands are a necessary component of the Nutrient Reduction Strategy. This research site has been used by Iowa State University every year since 1989 and has contributed to developments in nutrient management practices, including cover crops.
A total of 300 ADWs have been registered with the state. In 1997, Iowa passed legislation requiring all ADWs to be closed. This legislation also created a fund for cost-sharing closure of ADWs. Funds have been allocated to the program nearly every year since 1999.
To date, a total of 165 ADWs have been closed (including 12 under construction) from this program. The total costs incurred to close these ADWs, including those under construction, are estimated around $23.6 M. Cost share funds have provided $15.6M of these costs. Another 99 of the 300 ADWs were determined to be non-functioning or natural sinkholes by IDNR or were closed by the landowners using other funding sources.
When an ADW is closed, frequently a new tile system is needed to replace it.
Presently, 36 ADWs remain to be closed. These wells remain in operation through continued use permits issued by the Iowa Department of Natural Resources. Seventeen of those wells will be closed over the next two years if the budget request of $3.84 million over that timeframe is approved by the Legislature and the Governor. Many of the 19 remaining ADWs have unique challenges that will require innovative solutions. The remaining active continued use permits expire in 2019 and 2020. If resources are available and landowners are ready to proceed, it is expected that most, if not all of the remaining wells will be closed by that time.