## 4 Groundwater Management
### Arsenic Contamination  
Rural people in Bangladesh use a hand pump called a tube well to extract groundwater for drinking and other household purposes. The tube well consists of a tube (usually 5 cm in diameter), which is inserted into the ground (at a depth of \(<\)200 m) to tap the aquifer and is capped with a steel casing [41]. People in Bangladesh rely on tube wells as a safe source of drinking water compared to river/pond water [42]. This is generally the only source of drinking water in rural areas and was endorsed by the government and aid agencies, such as UNICEF (The United Nations Children's Fund), since the 1970s [41].  
The presence of arsenic in groundwater and its impact on human health was first identified in the 1980s in the neighboring West Bengal, India, [43; 44]. Skin diseases, including changes in pigmentation on the chest, arms, and legs and keratoses on the palms and feet were observed. Some of the patients examined by [PERSON] et al. [43] were from Bangladesh, which raised the alarm that similar arsenic contamination may already have occurred in Bangladesh. In Bangladesh, the presence of arsenic in groundwater was first identified in 1993 in Chapai Nawabganj district, in the north-western part of Bangladesh [41; 45; 46]. However, no scientific communication was made by the government of Bangladesh in that year. In 1995, a group of researchers from the School of Environmental Studies, Jadavpur University, Calcutta, India, organized a conference to raise awareness of arsenic contamination in West Bengal and Bangladesh [47]. The conference paved the way to alert the aid agencies working in Bangladesh as well as the government of Bangladesh to check the quality of the drinking water for arsenic contamination. In 1996-1997, different research teams from Jadavpur University, India; Dhaka Community Hospital, Bangladesh; and the National Institute of Preventive and Social Medicine (NIPSOM), Bangladesh, surveyed to analyze water samples from tube wells for arsenic contamination in different parts of Bangladesh [41; 48].  
Samples of hair, nails, and skin were also collected to check for arsenic. In all of the samples, a high level of arsenic was found [41; 48]. In 1998, the British Geological Survey (BGS) conducted an extensive survey in 41 districts of Bangladesh and found arsenic in the water samples in the range of 50-300 ug/L, which was far above the WHO-approved standard of 10 ug/L [49]. In the same year (1988), the scientific community was informed about the severity of the arsenic contamination problem at a conference organized in Dhaka, Bangladesh [50; 51]. The conference was able to attract the attention of major international aid agencies, such as the World Bank, UNICEF, DANIDA, and BGS. The aid agencies then started to actively collaborate with the government of Bangladesh in the further identification of arsenic contamination and the mitigation measures [47].  
Currently, tube wells in 61 districts out of 64 districts are arsenic-affected [44; 49; 52]. Tube wells are marked according to the Bangladesh standard arsenic threshold level of 50 ug/L; the tube wells are marked green if the arsenic level in the tube well water is less than the threshold level and are otherwise marked red [47]. Different mitigation measures are implemented to fight arsenic contamination, which includes public awareness and alternative sources of water, such as arsenic removal plants, deep tube wells, ring wells, filters, rainwater harvesting, and pipe-line water supplies [53; 54; 55; 56]. Although the mitigation programs are improving the situation [56] and the percentage of the rural population with access to safe water has increased by around 87% as reported by DPHE [57], 13% of the water source is still under threat, with arsenic concentrations higher than the government of Bangladesh's defined threshold level.