SEEPAGE ESTIMATION FROM LINK CANAL IN PAKISTAN

Abstract

Numerous empirical and analytical techniques are available in the literature for determining seepage from canals. It was, however, noted that these methods are not applicable for determining seepage under conditions prevailing under link canals in Pakistan. This limitation is due to the major differences in the conditions prevailing in the link canal area and the conditions considered for derivation and application of the known methods. This study was undertaken to explore the possibility of using numerical techniques for estimating the seepage from link canals where the ground water across the canal is unsymmetrical and the regional ground water table is sloping predominantly in one direction. A numerical model was developed to simulate the regional ground water flow and the canal seepage which was considered as a point source at the canal section. A sand model was also constructed to simulate the affects of seepage from the link canal on the phreatic surface of the regional ground water flow. The numerical model was verified against the results obtained from the sand model. The canal seepage under field conditions was then estimated in an inverse procedure by executing the numerical model with varied seepage recharge at the canal section until the phreatic surface computed by the numerical model agrees fairly with the field measured phreatic surface.