Hydrogeological Assessment of Siraha District, Nepal

Groundwater is precious natural resource that has direct linkage with the livelihood of the people. The Nepalese Terai lying in the southern part of the country is the northernmost extension of Indo-Gangetic Plain that can be considered as having major groundwater reserve that has been significantly exploited to meet the domestic and irrigation water demand. Siraha district lies in the eastern part of Nepal and is highly populated. The southern part of the Siraha district is represented by Terai Plain with vast agriculture land and groundwater is being exploited principally for domestic and irrigation purposes. However, the study for proper understanding of the groundwater resources in the area has not been carried out so far and hence the present study is aimed to assessment of groundwater resources in the area. Information from 37 lithologs of the deep tube wells was analyzed to assess distribution of subsurface materials in the study area. The southward fining succession is seen in the lithological sections drawn from the borehole lithological data. In most of the study area, the coarser materials like sand and gravels are distributed more than 50 percent in average, within the drilled depth. Aquifers in the study area are both unconfined and confined types. The transmissivity is high in the middle part while water level is high in the southern part of the study area with the general flow of groundwater from north to south.