Water table management on a watershed scale

CROPS are grown on nearly 20 million acres of poorly drained soils along the Atlantic Coast and Gulf States (21). In many of these states, cropland drainage has been one of the most important components of land management, Many of these artificially drained soils are adjacent to environmentally sensitive and ecologically important estuarine waters. Agricultural runoff has been implicated in the degradation of water quality and the potential destruction of many saline primary nursery areas (14,20). Agricultural production is important to the region, but it has become obvious that future agricultural practices must be designed and managed with water quality in mind. Excessive soil water is a major concern on poorly drained soils. In humid regions, artificial drainage is necessary to facilitate seedbed preparation and planting (spring trafficability criteria) and to minimize yield reductions from anaerobiosis. In general, drainage systems have been designed to lower the water table sufficiently to satisfy extreme drainage conditions 80 percent of the time. For most crops, there is an optimum planting date (22). Yields fall when planting is delayed past that date. The most extreme conditions, that is, the wettest periods, occur during the early spring in most years. During this period, evaporation …