Research

Impact of climate change upon groundwater resources in water limited environments (WLE)

Climate change is a continuous process over the long period of time. Rainfall variability and temperature change are the most significant variables in estimating impact of climate change on hydrology. There is strong evidence of climate change around the world due to both anthropogenic activities of emitting green house gases and natural phenomena. The global warming process creates the increase of temperature and rainfall distribution in most of the regions of the world. Groundwater resources, the primary source of water use in many regions, are under pressure due to these changes. Precipitation can vary in frequency and intensity. This affects groundwater recharge. On the other hand, increase of temperature causes evapotranspiration process in an area. This study is aimed at evaluating impact of climate change on the groundwater resources in water limited environments where it is in more vulnerable condition because of limited water resources.

In homogeneous unconsolidated porous media, recharging rainwater often moves through the unsaturated zone by a process similar to piston flow. Groundwater in recent and quaternary formations in many parts of the world conforms to this process, and unsaturated zones are likely to contain an accessible record of water and solute movement. The unsaturated zone contains not only information that can enable estimation of aquifer recharge, but also an archive of recharge history. The length of the record preserved in such profiles will depend on several factors, mainly a) the depth of the unsaturated zone, b) the moisture content, c) the recharge rate etc.

The methodology includes the evaluation of the past climatic variation of few thousands or hundreds years with the unsaturated zone record of solute movement process, linking with the recent climatic variables with groundwater flow and transport modelling, and deriving future scenarios of climatic variables from the trend of past and recent climate changes. For solute movement process chloride will be used to estimate the paleo-groundwater recharge and thus precipitation can be inverted from the recharge as a part of precipitation. A solute transport model will be developed further with pyEARTH-1D and pyEARTH-2D model for unsaturated zone coupling with MODFLOW and MT3DMS. Fully-transient-state groundwater model will be run using MODFLOW for last fifty years from when the meteorological data are available. Based on these unsaturated and saturated models, future climate variables scenarios will be derived and evaluated their impacts on system response of groundwater resources in water limited environments.