Mitsch and Gosselink(2000) presented potential nutrient retention rates per area of marsh or wetland ranging from 3 -66 g N m−2 y−1 and 0.36-5.6 g P m−2 y−1. In existing dairy operations, most of the aerobic ponds range from 4 -14 hectares in size and utilize 4 : 1 pond levee slopes, thus providing approximately 450 square meters of littoral zone per hectare of pond.