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Impacts of Salinity, Arsenic, and Drought in Southwestern Bangladesh

M. A. Abedin
Bangladesh Agricultural University, BAU and Department of Soil Science PhD and Postdoc, Kyoto University and Postdoc, UK

Umma Habiba
Bangladesh Agricultural University, BAU

Rajib Shaw
Keio University | Keidai · Graduate School of Media and Governance Doctor of Science

Abstract/ Executive Summary:

The southwest area lies between 21º30' and 23º15' north and 89º 00' and 90º 00' east and includes the world’s largest continuous mangrove forest, the Sundarbans, as well as estuarine marshlands and numerous rivers, canals, and their tributaries (Giri & Shrestha, 1996; Viju, 1995). It covers an area of 26,200 km² and has a population of 18.3 million. It is divided roughly into coastal and inland areas. The terrain is relatively flat; the elevation ranges from sea level to 5.0 m above mean sea level (Castro-Ortiz, 1994). Approximately 85% of the people of this region depend on agriculture; landless farmers make up almost 66% of population. Fishing, agriculture, shrimp farming, salt farming, and tourism are the area’s main economic activities. The southwest region – especially Satkhira, Bagerhat, Khulna and Jessore – experience extreme inland saline-water intrusions, and agricultural crop fields gradually experience this salinity increase. Another hazardous problem is severe arsenic contamination in groundwater. In recent times, arsenic in tube-well waters has so upset drinking-water supplies that it became a national health issue. The groundwater is contaminated by arsenic in a large area, mainly around major rivers in this region. Similarly, the silent, invisible disaster drought appears in this region. The average annual rainfall in this area is approximately 1,700 mm, and the rainfall of the district along the border with India at the west is fairly low. Severely decreased Ganges water discharge along with the river’s low flow rate in the dry season causes drought in this area and damage to the mangrove forest. Furthermore, the presence of Farakka Dam on the upper Ganges River and depleted groundwater, this region is more prone to drought and designated as a moderate drought-prone area in Bangladesh. But sinking groundwater tables are more frequently observed in Kushtia and Jessore districts. The high-salinity, high-arsenic, and drought-prone areas of southwestern Bangladesh are represented.

Keywords: Natural hazards, Southwestern part of the country, Pertinent underlying causes, Overall impacts, Interrelationship, Natural hazards, Appropriate future strategies, Effectively overcoming

Location: Satkhira, Bagerhat, Khulna and Jessore district, Bangladesh

Start Date:

End Date:

Program Area: Risk Management in Agriculture

Commodity: Drought, Arsenic, Water salinity

Objectives:

To explore the current situation of the previously mentioned natural hazards in the southwestern part of the country, their pertinent underlying causes, overall impacts and interrelationship among these natural hazards, and appropriate future strategies for effectively overcoming these conditions.

Methodology:

Existence of Farakka Barrage: In 1974, India built the Farakka Barrage, diverting water from the upper sections of the Ganges River and into the Hugli River (Gain, Aryal, Sana, & Uddin, 2007). The effects downstream in Bangladesh included a significantly decreased water supply, which led to increased intrusions of seawater into the Ganges River basin and eventually increased river and groundwater salinity (Gain et al., 2007; Shamsuddin, Xiaoyong, & Hazarika, 2006). Sea-Level Rise and Salinity Intrusion: One direct consequence of sea-level rise is intrusion of salinity with tides through rivers and estuaries. Intrusion would be more acute in the dry season, especially when freshwater flows from rivers would diminish. According to an estimate of the master plan organization, about 14,000 km2 of coastal and offshore areas have saline soils and are susceptible to tidal flooding. If some 16,000 km2 of coastal land is lost because of a 45 cm rise in sea level, the salinity front would be pushed further inland. The current interface between freshwater and saline water lies around 120–160 km inland in the southwest, and this could well be pushed northward as far as central Jessore region in the event of a sea-level rise (ADB, 1994). Horizontal Expansion of Shrimp Farming: Industrial shrimp cultivation is one prime reason why this high-salinity area is increasing and intensifying over time. The rapid expansion of shrimp farms during the last decade, along with the adoption of extensive and improved farming techniques, is partly responsible. According to Islam, Sattar, and Alam (1999), salinity in shrimp-cultivation areas may be 500% higher than in areas without cultivation. Salinity Intrusion in the Coastal Rivers: As sea level continues to raise, the associated effects of permanent inundation are likely to increase salinity near coastal areas. A recent study shows that 5 ppt saline front will penetrate about 40 km inland for SLR of 88 cm, which will affect only the freshwater pocket of Tetulia River in Meghna Estuary. Ingression of Soil Salinity: Salinity ingress causes an increase in soil salinity, especially when farmers irrigate their lands at the beginning of the low flow period. This paper shows increases in soil salinity in the southwest region. The Soil Resources Development Institute (SRDI) (1997) reported that soil salinity levels south of the towns of Khulna and Bagerhat ranged between 8 and 15 dS/m during the low flow season.

Source of Information: Community, Environment and Disaster Risk Management, Volume 9, 165–193; ISSN: 2040-7262

Article Link (Online Journal): doi:10.1108/S2040-7262(2012)0000009016

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The findings of this study provide a detailed overview of various types and intensities of natural hazards faced by different communities in southwestern Bangladesh as represented by three selected measures: increased salinity, arsenic contamination, and drought. All of these natural hazards have multiple impacts on communities, decreasing their survivability and increasing their vulnerabilities to future events. Moreover, according to IPCC (2007), the effect of climate change on surface and groundwater resources in Bangladesh will be entirely negative. From the study, it is clear that the southwestern region faces water-related problems from too much water in monsoon season (leading to flooding) and too little water in dry season (leading to drought). People in this area depend on surface water for fish cultivation, navigation, and industrial and other uses, and they use groundwater for domestic and irrigation purposes, so the presence of saline and arsenic in water – along with water scarcity during the dry season – means that the lack of safe drinking water and irrigation water ultimately hampers their daily lives.

Knowledge Management: Journal