Development of Surface Groundwater Interaction Model using MODFLOW for Mohenjo-Daro World Heritage Site

Abstract

The Archaeological Remains of Mohenjo-Daro, a world heritage site, are located on the west bank of Indus River about 510 km North-East of Karachi and 27 km away from Larkana district of the Province of Sindh. The major cause of deterioration of the ruins of Mohenjo-Daro is due to high water table, which is of two types. The first is mere saturation of structures and second and more destructive phenomenon is that rising moisture from high water table acts as carrier of salts from ground to the surface of the monuments. More serious is the aspect of transportation of minerals salt associated with rise of water table. While moisture evaporates, the dissolved salts are left on the surface. At this site, Sodium Sulphate, Magnesium Sulphate, Nitrates and other associated Chloride and carbonates are expected. Both physio-chemical and physical processes play their role in monument disintegration. As the site is susceptible to flooding from surface and ground water sources, therefore, it is required to identify the technical solutions for ensuring the future safety of the site from escalating water table and salinity. Piezometer data was collected from Water & Soil Investigation Laboratory Mohenjo-Daro, rainfall & evaporation data was collected from Pakistan Metrological Department. Irrigation data, levels and discharges from downstream Sukkur Barrage and levels of Dadu Canal was collected from Irrigation and Power Department, Government of Sindh. After acquiring the raw data, it was converted into the required form. This data was analyzed manually and then it was modelled on MODFLOW. The results of both manual and model analyses were found out to be similar. It was found out during the study that the Indus River and Dadu Canal both acts as a sink or source depending on their water level causing the water to flow through the site. It was also found out that the water quality is saline at the site and improves when one moves away from the site. The explanation behind saline groundwater may be because of the way that the study range is limited between two surface water bodies i.e. Indus River on eastward and by Dadu Canal on west side. Different piezometers were installed at the site with screen groundwater. At present simply five piezometers are in working conditions and the rest are non-functional. The five piezometers which were functional had a typical water table of something like 15 ft. Noticeable water sources observed in the study area were the Indus River and Dadu Canal along with fish farms, paddy plantation and to some degree precipitation. Paddy XV plantation around the study area is found to increase the groundwater level of the region. Misfortunes at and around study range incorporates evapotranspiration (from vegetation, trees, crops, and so forth.), dissipation from water bodies (river, canal, fish farms, and so on.) because of high temperature & wind, reflection of groundwater and pumping of water straight forwardly from stream for watering system. Amid the visit it was watched that burrowing of earth material from the Indus couch for development of street was in advancement. The expulsion of earth from the Indus couch will leave a despondency in the waterway accordingly welcoming the stream to quicken its disintegration towards the site. Site is unfavorably influenced by far reaching water leakage and detritions. The water table likewise began rising after the introduced tube wells were abandoned. In 2006 the water table was at 9m beneath the plain level. Then again, the capillary rise climbed over the water table at Mohenjo-Daro was more than 3m. Till November 2011, the water table vacillation was somewhere around 14 and 20 feet subterranean surface.