High rate irrigation for groundwater recharge
Date
2006-10
Authors
Emond, Henriette M., author
Madison, Mark F., author
Sinclair, Frank, author
U.S. Committee on Irrigation and Drainage, publisher
Journal Title
Journal ISSN
Volume Title
Abstract
With the establishment of Total Maximum Daily Loads (TMDLs) for Oregon rivers and increasingly stringent regulatory limits on surface water discharges, municipalities are faced with mounting challenges on discharging effluent. Effluent containing relatively high temperature levels or nutrients cannot be discharged to rivers during times of low flow, principally in the summer. To address this issue, municipalities are examining other alternatives for treatment and discharge. This paper highlights the benefits of a wastewater treatment alternative using a high rate effluent irrigation system and provides a description of a study that is being used to validate those benefits. In the study, wastewater is applied to a crop at rates greater than agronomic rates and is allowed to percolate below the root zone for eventual groundwater recharge and ultimate groundwater discharge to the nearby river. As the water slowly moves through the root zone, nutrients in the water are transformed in the soil and are taken up by the crop. The water temperature is also cooled through the interaction with the groundwater. The potential benefits from these systems include: increasing the amount of wastewater that can be applied per unit land area; improving the water quality of excess effluent irrigation water moving through the root zone which ultimately recharges groundwater and discharges to the river; and increasing the amount of water supporting the river flow as compared to strictly agronomic rate irrigation over a greater land base. A high rate effluent irrigation program is being evaluated at two different sites in Western Oregon to collect data on this concept. The information will be analyzed to evaluate the performance of a poplar tree reuse system in polishing advanced secondary treated wastewater to remove nutrients and increase the quality of water. During the summer growing season, plots will be irrigated at 100 percent, 150 percent, 200 percent, and 400 percent of agronomic rates. Data will be collected to monitor the soil moisture and the vadose zone water quality associated with each of these rates of irrigation, in the root zone and just below the root zone. Installation of irrigation and monitoring equipment for the study was begun during the summer of 2005 and 2006. Data will be collected and analyzed through the spring, summer, and fall of 2006 and 2007. Preliminary results should be available by October 2006.
Description
Presented at Ground water and surface water under stress: competition, interaction, solutions: a USCID water management conference on October 25-28, 2006 in Boise, Idaho.