The interrelationship of salinity and land use in the Khulna Division, Bangladesh

Abstract

Bangladesh is a very poor and populous country located in Ganges-Brahmaputra-Meghna (GBM) delta, one of largest deltas of the world. The GBM consists of a low-lying flood plain where the local population mainly cultivates rice, fish and shrimp. However, safe water options for drinking water and agricultural purposes are limited in the GBM delta. In the past a shift from rice cultivation to aquaculture has been made, whereas on the long-term aquaculture could increase salinity, making safe water even scarcer. So, salinization should be kept at a minimum to ensure safe water for the population. Therefore, this study aimed at identifying the relation between land use, agriculture and rice in particular, and salinity. Remote sensing data was used to make a land use map. 72 soil samples, 73 water samples from boreholes and 115 water samples from the aquifers were taken. In addition, 106 surveys were held to obtain data on farming practices and for validating the land use map. These data were analyzed using a set of T-tests. Firstly, it was found that aquaculture is increasing over the past decades. Secondly, it was found that salinity is decreasing with respect to latitude. Thirdly, it was found that soil salinity, groundwater salinity at the water table and surface water salinity is related to certain land use types. Here aquaculture is mostly located in areas of high salinity and rice is located in areas of low salinity. No relation was found for land use with respect to shallow groundwater. Fourthly, it was found that land use correlates with elevation which can be explained by the fact that higher laying terrain floods less often with saline water. Therefore, aquaculture is more suitable to be cultivated in the low lying terrain. Lastly, no relation was found between the age of a certain land use type and salinity. This study confirmed that there is an interrelationship between land use and salinity. However, the direction of the relationship cannot be proven. More research is needed to identify if salinity is a driver for land use change, if land use change is a driver for a changing salinity or if the effects of both land use and salinity are amplifying each other.