Effect of Pipe Pressurization on the Discharge of a Tile Drainage System

Abstract

Predicting the drainage impacts on downstream peak events is complex because it involves studying many physical processes at different interdependent scales: the individual field, the drainage network, and the catchment. This study focused on an experiment performed in a small subsurface‐drained catchment (130 ha), east of Paris, France. The main objective was to study the influence of the temporary pipe pressurization of the drainage network on the field drainage discharge during intense rainfall events. The flow rates at one buried pipe collector within the drainage network and at the catchment outlet were monitored concurrently with the pressure head in the pipe. Water levels were recorded in rows of piezometers aligned between drains connected to the studied collector so that water storage in the water table could be investigated during pipe pressurization. Two years of observations showed that when a pipe pressurization condition existed, the collector discharge was limited or reversed and the infiltrated water was temporarily stored within the field soil as the water table rose. Between the usual stages of normal subsurface drainage (peak flow and recession), two additional behaviors appeared to occur, similar to those resulting from implementing controlled drainage and subirrigation practices, and with noticeable consequences on the discharge hydrograph. No strong relationship could be established between the collector discharge limitation and the catchment hydrology, probably because pressurization affected only a small part of the drainage network.

Artificially Drained Catchments—From Monitoring Studies towards Management Approaches

“…From a hydraulic perspective, drainage discharge is regulated not only by the upper boundary conditions, such as rainfall and evapotranspiration, but also by the pressure conditions in the collector pipes (Henine et al, 2010). In cases of pressurization (i.e., when a positive head builds up in the drainage system because of intensive rainfall or backwater effects), discharge is limited or even reversed.…”

Effects of Climate Change on Hydrological Indicators of Subsurface Drainage for a Representative French Drainage Site

“…The regime from the relation Q spe f(RP) is characterized by two different linear regimes split by a breaking point close to 2 years, due to design criteria in order to intercept a rainfall of 15 mm d −1 (Augeard et al, 2008;Henine et al, 2012). Above this value, the pipe is pressurized (Henine et al, 2010) and the specific discharge may be strongly reduced (Nedelec, 2005;Henine et al, 2012), according to the size of the networks and depending on the intensity of the event. If the RP of the breaking point decreases, the size of the networks might be considered as no longer suitable to fulfil efficiently their flood protection function.…”

Mapping of 30-meter resolution tile-drained croplands using a geospatial modeling approach

“…Compared to undrained cropland, tile drainage also causes significant changes in watershed hydrology 4 , 5 . Studies have shown subsurface drainage removes excess water from the rootzone 6 , results in higher infiltration and lower surface runoff 7 , peak flows 8 and flooding 9 . Tile drainage tends to increase the watershed baseflow 10 , 11 , decrease groundwater travel times 10 , 12 , increase annual runoff volume 4 , 13 – 16 , and increase instream nitrate concentrations 4 , 8 , 17 , 18 .…”