University of Twente Student Theses


Net recharge dependency on land cover type

Ginting, Yuliana (2013) Net recharge dependency on land cover type.

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Abstract:Groundwater is an important renewable resource. The largest freshwater in the earth, about 95%, is stored as groundwater. According to Dripps and Bradbury (2007) recharge is the entry of water into saturated zone. Therefore responsible for replenishment of groundwater But in dry climate such as in semi-arid condition, groundwater evapotranspiration (ETg) is high and is reducing the recharge (Rg). The difference between Rg and ETg called net recharge (Rn) determines replenishment of groundwater resources and therefore also the sustainability of groundwater resources (Lubczynski, 2006). The aim of this research is to assess the dependency of net recharge on land cover type in the Sardón catchment in Spain. A small patch (419,3 m x 239,3 m) within the Sardón catchment has been selected as NRZ (NRZ). The total area of the NRZ was 10039 m2 which consisted of 93889 m2 of bare soil, 4110 m2 of Quercus ilex and 2340 m2 of Quercus pyrenaica . The NRZ has uniform soil type and water table depth required to focus the research on dependency of net recharge on the land cover type. The net recharge of different land cover types within the NRZ is modeled using HYDRUS 1D. HYDRUS 1D numerically solves the Richards equation and simulates water flow in the unsaturated zone. Simulations were performed in two different periods. The first period was used for calibration and it simulated 142 days, starting from 08/02/2009 until 29/06/2009. The second period was used for validation, simulating 162 days starting from 28/12/2009 until 07/06/2010. In order to compare the soil water fluxes in year 2009 (calibration period) and year 2010 (validation period), from both time series we chose the same periods starting at 15th February until 7th June to perform the model simulation In both years the net recharge was negative. In 2009 the values of the net recharge were -203.29 mm for bare soil, -0.03 mm for Quercus ilex and -0.02 mm for Quercus pyrenaica. In 2010 the values of net recharge were -165.00 mm for bare soil, -58.9 mm for Quercus ilex and -53 mm for Quercus pyrenaica. The negative value of the net recharge for both selected years means the ETg in this area was much higher than the recharge mainly at bare soil land cover type. This observation is understandable because the NRZ is located in the discharge zone of the Sardón catchment. The differences between net recharge responses at the three different land cover zones imply that the land cover type has a great impact on net recharge and furthermore on groundwater resources.
Item Type:Essay (Master)
Faculty:ITC: Faculty of Geo-information Science and Earth Observation
Programme:Geoinformation Science and Earth Observation MSc (75014)
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