EFFECTS OF DRAIN ENVELOPE AND SLOPE ON PERFORMANCE OF A DRAINAGE-SUBIRRIGATION SYSTEM.

A field study was conducted to determine the effect of fabric wrap envelope and drain slope on the performance of a combination drainage and subirrigation system. Data were analyzed by examining relationships between flow rate and midpoint water table elevations. An entry resistance was defined and its value for each pair of 9,100 data points for drain flow rate versus water table elevation midway between the drains. Analyses were conducted to determine if the entry resistance changed with time after the drainage system was installed. Results of the study showed that the effect of slope and envelope on drainage and subirrigation varied somewhat depending on field location. However, an analysis of the data led to conclusions that the paper discusses.