Water

A running theme of these blogs has been potable water or rather, the lack thereof, in Bangladesh. The coastal conditions in Bangladesh are heavily influenced (as is every other geological condition in Bangladesh) by the monsoons the region experiences. The coastal conditions affect much of the coastal areas and even slightly further inland. The storm surges which occur during tropical cyclones which hit the coast of Bangladesh move weaken the coast and erode I making it more vulnerable to weather conditions.  Storm surges also push salt water from the ocean into the delta which then becomes brackish, undrinkable, unsuitable for crops, and detrimental to the soil conditions for years to come. When the storm surge brings salt water into the delta, it does not get washed away sufficiently. In fact, it may continue to ebb into the delta becoming a larger and wider-spread problem in years to come.  

The above is a general overview; however, one can easily predict the size of the snowball such conditions could cause. As it happens, much of the ground water, especially further north, are heavily contaminated by arsenic which obviously make them useless for drinking water as well as crop growth.  Interestingly, I read several academic publications regarding these issues to write this and all of them mentioned arsenic poisoning being a problem but I did not quite understand where the arsenic was coming from. It turns out that the tube wells which Bangladesh uses to retrieve ground water are to blame. Tube wells are wells which are formed by drilling large pipes or tubes into the ground and pumping the groundwater up through them with the use of an electric or gas powered motor. It is a pretty simplistic design and it should have worked quite well except that back in the 1970’s a clean water campaign drilled a huge number of these wells into layers which already contained toxic amounts of naturally occurring arsenic.  http://science.time.com/2010/06/19/study-says-arsenic-poisons-millions-in-bangladesh%E2%80%94but-theyre-not-the-only-ones/

This leaves only a few water options left: lakes, rivers, and other wells which are not contaminated by arsenic. The problem is; many of those bodies of water including the wells have extremely high salinity levels. Due to subsidence in the delta, the water table aquifers are shrinking which means that ground water is harder to come by and harder to replenish when the rains do come.

The water issue aside, as the coastal region is eroded it becomes more vulnerable to storm surge. As mentioned in my previous entry, storm surge is the most dangerous aspect of the tropical cyclones which fairly regularly make landfall in Bangladesh.  Sea level rise, as one would expect, has made these tidal and storm surges even more devastating. Even as sea level rises, it starts to bleed into the delta contributes saline to the delta. Currently Mangrove forests help protect the coast and hold sediment together with their root systems. There have been some interesting advances in attempting to use oysters as a sort of natural reef which would also accumulate sediment.  An oyster reef, if properly maintained, would potentially provide a solid source of coastal food- an oyster farm- and it would help reinforce the coastline and protect the mangroves.

http://www.royalhaskoningdhv.com/en-gb/projects/cultivating-oysters-to-combat-coastal-erosion-in-bangladesh/107

There have been some other, more concrete ideas as to how to mitigate the negative effects of tidal flooding such as; embankments, sluice gates, and changes in what the agricultural community grows seasonally. These all will hopefully help prevent salinity levels from rising inland. Soil salinity is difficult to combat because many of the mitigation tactics meant to prevent saline water from moving further inland into the deltaic zones involve planting sturdy vegetation which can also be consumed by the population and unfortunately, it is virtually impossible to grow anything in the soil near the coast because it is simply too salty to support the usual, climate-appropriate crops.

http://www.pakbs.org/pjbot/PDFs/38%285%29/PJB38%285%291359.pdf

http://teacher.buet.ac.bd/msalamkhan/teaching_msk_files/coastal_issues_bd.pdf