Assessment of Dynamic Groundwater Reserve of Kamarup District Lower Assam, India

Abstract

Despite sufficient rainfall, a large portion of the northeast region of India suffers from water scarcity especially during dry seasons when groundwater acts as a significant source of water supply. Consequently, a proper assessment of groundwater condition at a district/block level is very much essential to adopt sustainable water management practices. Additionally, climate change and crossborder water disputes generate new challenges in the water management of Northeast India. In this study, an attempt has been made to present groundwater scenario of Kamarup district in lower Assam as a case study representing North-East India. For this purpose, we used the available temporal groundwater-level data derived from observation wells at five sites namely Agyathuri, Azara, Bamunigaon, Khara and Rangia located in the Kamrup district (lower Assam) of north-east India. The dynamic groundwater reserve (DGWR) has been estimated for the period from 1996 to 2006 using groundwater level data from these five sites along with monthly rainfall data and published pumping test data. This will help to analyze the groundwater dynamics of the study area. In order to cross check the obtained results, we used terrestrial water storage changes (TWS) derived from GRACE (Gravity Recovery and Climate Experiment) satellite data. TWS is a satellite-based monthly mean liquid water equivalent thickness with one degree spatial and monthly temporal resolution available from 2002. Terrestrial water storage includes the soil moisture, surface water equivalent and groundwater anomaly based on satellite observations of earth gravity field from the (GRACE). In the present study, TWS data was analyzed for over a period of 5 years from 2002 to 2006. The results of the study indicate that the maximum groundwater fluctuation was in the range of 0.84 to 3.48 m and minimum between -5.07 to -1.47m. Over the entire study area, we observed a decrease in dynamic groundwater reserves. From the trend analysis, it is obvious that there is an increasing trend of groundwater level at Khara, Rangia and Bumungiaon site and a decreasing trend at Agyathuri and Azara site. Further, the DGWR results showed that two sites (Agyathuri and Azara) were continuously subjected to stress from 1999 onwards. We observed that the DGWR and TWS are showing a comparable negative trend in the dynamic groundwater storage capacity for the study period. In the year 2004 the recorded TWS and estimated average_DGWR are relatively high during the study period. Thus, the results of this study provide a clear picture of spatial and temporal variations of dynamic groundwater resources in the study area, based on which important recommendations can