Empty Drain and the Water Level at Midway between the Drains. Aspects Regarding Management

Abstract

Standing water above drains as a result of a submerged drain outlet, promotes flow conditions so that there is a smaller rise in the water table height at midway between the drains. This case has been studied through theoretical analyses by van Deemter (1950); Childs (1958), Kirkham(1958); Santos-Júnior (1971); Wessseling (1979) an Gammal et al (1995). In this paper the numerical results from DRENAFEM software package simulator are compared with the theoretical analysis of Santos-Júnior (1971). The software uses a finite element analysis to solve the Richard´s equation. Several simulations were performed with a small drain radius, and with a back pressure in the drain outlet to achieve a high entrance resistance and promote the rise of the water table at midway between the drains. With the standing water above the drains, the theoretical and numerical results show a rise in the water table height which is smaller than the drain outlet pressure. This paper demonstrates how the software can be used to simulate the behavior of a water table under controlled drainage to determine the water table's position in situations with no analytical solutions, such as hydraulic conductivity anisotropy or in non-homogeneous soils with several layers.