Adhikary, Sajal Kumar, Das, S. K, Saha, G. C and Chaki, T (2013) Groundwater Drought Assessment for Barind Irrigation Project in Northwestern Bangladesh. In: 20th International Congress on Modelling and Simulation (MODSIM 2013), 01 December 2013-06 December 2013, Adelaide, South Australia.

Abstract

Natural droughts are recurring phenomena that usually affect nearly all components of the hydrological cycle. Groundwater (GW) drought is a particular type of hydrological drought. It is generally caused when the GW heads in an aquifer fall below a critical or threshold level over a certain period of time due to natural and/or human induced causes and interventions. In the recent past, there was increased frequency of droughts in Bangladesh. Particularly, the northwestern region of the country was severely affected by the occurrence of droughts and high variability in rainfall. The country’s largest groundwater-fed irrigation project, Barind irrigation project is located in this region, wherein about 75% of irrigation water comes from the GW source. The national water policy of Bangladesh has also suggested the GW development for irrigation in both the public and private sectors. Therefore, it is essential to investigate the occurrence and distribution of GW drought severity for the effective GW resource management of the Barind Irrigation Project in the northwestern Bangladesh. Barind Irrigation Project is located within the Barind Tract area, which covers most parts of seven northwestern districts, namely Bogra, Dinajpur, Joypurhat, Naogaon, Pabna, Rajshahi, and Rangpur under Rajshahi division in Bangladesh. Barind Multi-purpose Development Authority (BMDA) reported that 6000 deep tube wells and 66000 shallow tube wells were installed by the year of 2000 for irrigation development. The GW dependent irrigation system in the area has reached a critical phase as the GW level has dropped below the depth of the shallow tube wells in many places. The recently published GW zoning map indicates that a record of 60% irrigated croplands in Naogaon district have become critical for shallow tube well operation. The overexploitation has caused the GW level falls to the extent of not getting fully replenished by the rainfall recharge. If this over-utilization of the Barind aquifer continues, it may result in its exhaustion after few years that will have certain impact on the agriculture-based economy of the country. Hence, the main objective of this study is to assess GW drought at a specific part (Naogaon district) of Barind Irrigation Project in the northwestern Bangladesh, where GW scarcity is increasing day by day. Available GW level and climate (rainfall and temperature) data are collected from the relevant organizations in Bangladesh. The cumulative deficit (CD) approach from threshold GW level is applied to evaluate the drought severity. Different threshold levels (70%, 80%, and 90%) of the mean GW level for the whole area are computed to visualize the drought severity in the GW system. The estimated CD values at different monitoring wells are interpolated in the ArcGIS platform to produce the spatial GW drought maps, each of which represents the drought severity for each specific threshold value. Meteorological drought has been computed by the Standardized Precipitation Index (SPI) method and wet events are identified from time series data of precipitation. The SPI is used to identify any likely relationship of GW drought and wet events with the GW level. Similarly, temperature records are used to explore any possible connection between GW and climate in the study area. Spatial maps of GW drought for different threshold levels indicate that GW drought is a frequent event in most part of the study area and the northern part is free from drought events. The GW hydrographs for most of the monitoring wells exhibit significant declination of GW table in the study period because of the extensive GW withdrawal from the underground aquifer, which is the main reason for the GW drought occurrence. The study finds that GW drought is correlated to the meteorological drought event, which indicates that the deficiency in rainfall may exacerbate the GW drought conditions. The study finally recommends that development and conjunctive use of GW and surface water resources should be undertaken and practiced to satisfy the increased irrigation water demand in the Barind Irrigation Project as well as to reduce the growing pressure on the GW reserves in northwestern Bangladesh.

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