Designing In-Field Water Storage for an Agricultural Subsurface Drainage System

Abstract. Subsurface (tile) drains installed on agricultural land with poor natural drainage allows timelier field operations and generally contributes to improved crop yields. Concerns over water quality and hydrologic impacts caused by subsurface drainage have led to an opportunity to improve some aspects of the practice. The overall objective of this project is to design, install and demonstrate long-term water quality and quantity impacts of controlled drainage practices in the Red River Valley of the North and increase the acceptance and adoption of the practices among producers and other stakeholders. In this document we will discuss the project background and system design. The project include two field sites in northwest Minnesota, USA. Site 1 utilizes an instrumented watershed approach where a 63 hectare (0.63 km2, 155 acres) field parcel is divided into a control and two treatments with i) controlled drainage, ii) conventional subsurface drainage, and iii) surface drainage only (control). Site 2 is a 26 hectare (0.26 km2, 65 acres) parcel with two zones managed with controlled drainage, and one zone featuring a saturated buffer. Installation of the below-ground drainage components and water control structures was completed in the fall of 2015. Surface and subsurface runoff quantity are monitored continuously. Water samples are collected using automated water samplers and analyzed for nitrate-nitrogen. Meteorological information is collected using an automated agricultural weather station located within 3 km. The meteorological information enables the calculation of crop water use utilizing the standardized Penman-Monteith equation and will support establishing the field water balance.