Author(s): Mohammad Zare; Manfred Koch
Linked Author(s):
Keywords: Miandarband plain; Iran; Groundwater flow modeling; Irrigation; Water logging
Abstract: The Miandarband plain is one of the most fertile plains of the Kermanshah province, Iran, as it is endowed by ample surface and ground water resources. With the construction of irrigation and drainage networks and the reduced use of ground water resources, the ground water table has risen and caused water logging, followed by salinization of the arable soils in the plain. Environmental deterioration and economical losses have been the consequence. From this the importance of a study of the fluctuations of the water table levels in response to the construction of irrigation and drainage network in the Miandarband plain becomes clear. In this study the fluctuations of the groundwater table have been simulated in both steady-state and transient regimes using the 3D groundwater flow model MODFLOW within the GMS 6. 5 environment. For the set-up of the conceptual model, the meteorological, geological, hydrological and hydrogeological parameters, pertinent to the Miandarband area, were studied and implemented into the model. Based on the geological composition of drilling log cores, the aquifer is divided vertically into 11 horizontal layers. The groundwater surface measured in April 2007 is used to carry out the steady-state calibration and employed, at the same time, as initial condition for transient simulation with head measurements taken between May, 2007 and March, 2009. For model verification the heads measured in the subsequent month, April, 2009 is used. A very good agreement between simulated and observed groundwater heads with a coefficient of determination R2 of 0. 99 is obtained. In the next step the transient effects of the operation of the irrigation and drainage network on the ground water table is analyzed, whereby the simulations are started with initial conditions as they have existed prior to the operation of the irrigation/drainage network. In addition, to satisfy the needs of the proposed cropping pattern with the recommended surface irrigation, an annual water volume of 176. 2 MCM is transferred from the Gavshan dam to the Miandarband irrigation and drainage network. It is assumed that 25% of this irrigation water infiltrates into the aquifer as recharge. With these parameters ground water levels for times of 1, 5 and 10 years after the start of the network operation are calculated. The results show that after 1 year the groundwater table in the center of the plain has risen about 1. 8 m, but going up to 3. 2 and 5. 2 m for 5 and 10 years, respectively. Moreover, after 1 year, 6. 59% of the plain’s areas are waterlogged, a value which goes up to 37. 91% and 56. 28% after 5 and 10 years, respectively. In conclusion, by using a transient groundwater flow model it is possible to control the ground water levels and, so, to prevent the occurrence of detrimental water logging events in irrigated agricultural areas.
Year: 2013