Journal of Food, Agriculture and Environment

Determining the natural drainage coefficient of a region using hydraulic conductivity and conjunction of iso-potential lines: A case study of northeast Ahwaz, Iran

Author(s):

AbdAli Naseri, Yaser Hosseini, Mohammad Albaji ^*, Saeed Boroomand Nasab

Recieved Date: 2009-10-14, Accepted Date: 2010-01-03

Abstract:

The study of underground water movements and their applications are among the most important field of water hydraulics where the water flow typically is considered in three states: equilibrium state, steady state and non-equilibrium state. It is assumed that in the equilibrium state the water stability level in unconfined water-containing layer or pressure level in the confined layer will remain unchanged. They also will not change against time when the underground flow begins to move. In order to determine the inflow and outflow of the flow grid of a region, which includes flow lines perpendicular on the iso-potential lines of the underground water, is usually used. Considering the problems with depicting of the flow lines and the resulting unreliable flow grid, the present research attempts to determine the quantities of inflow and outflow to the specified region in northeast Ahwaz (Iran) by means of water volume differences in different months of the year. In order to calculate, first iso-potential lines of two consecutive months were overlapped and the resulting intersecting points were determined and then height differences of some of the points were obtained. The corresponding polygons were developed subdividing the total area into sub-areas with either minus or plus peizometric heights. After polygons developed and in order to determine the variations of the flow water volume, the sum of the polygon area by height difference of each polygon and the effective porosity resulted from hydraulic conductivity in the region was obtained. By dividing such resultant over the area of the region, the natural drainage coefficient of the selected months was obtained while its negativity indicated that the flow elevation reduced in the second month compared to the pervious month. This research indicated that outflow discharge is equal to 0.29 mm in day during months of late February to late April while it reaches to 0.84 in day during the months of late March to late May. During months of late April to late June this value amounts to 1.12 mm in day while during the months of late May to late July it declined to 0.39 mm in day. It should also be noted that inclusion of the natural inflow/ outflow of the study area near the river bank area is necessary in revising of the natural drainage coefficient for the region.

Keywords:

Polygons, peizometric, inflow, outflow, natural drainage coefficient, hydraulic conductivity, iso-potential lines

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Journal: Journal of Food, Agriculture and Environment
Year: 2010
Volume: 8
Issue: 1
Category: Environment
Pages: 389-393

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