Impact of climate change and management strategies on water and salt balance of the polders and islands in the Ganges delta

Author:

Mainuddin, Mohammed ; Karim, Fazlul ; Gaydon, Don ; Kirby, Mac

Date of Publication:

2021-03-30

Publication Type:

Journal Article

Journal Title:

Scientific Reports

Volume:

11

Issue:

7041

Part:

Full paper

Pages:

15

Abstract:

Crop production is limited in the Ganges delta due to the lack of freshwater and high salinity during the dry season. Enhancing crop production, particularly by growing a crop in the typically-fallow dry season is a key strategy for alleviating poverty in the region. We used a polder water and salt balance model to examine salinity and crop evapotranspiration at quantified for two sites in Bangladesh (Dacope and Amtali) and one site in India (Gosaba). We assessed the impact of several scenarios, including two cropping scenarios (one with a dry season or Rabi crop, the other without), a groundwater pumping scenario (to lower the salty groundwater table), two scenarios of control over the use of river water for irrigation (one preventing its use and one allowing its use irrespective of the salt concentration in the river) and one scenario of establishing a greater area of storage ponds and canals. In addition, five climate change scenarios were assessed together with one of increasing river salinity due to sea level rise. Dacope and Gosaba have lower rainfall than Amtali, and are saltier, with Gosaba being the saltiest. A key (and unsurprising) finding is that salt management is very important, particularly at the two drier sites, Dacope and Gosaba. Groundwater pumping to lower salty groundwater tables and to allow the storage of fresher water lowers salinity in the soil and ponds, as well as in the shallow groundwater, and leads to more irrigation. Conversely, allowing the use of salty river water for irrigation (which simulates a breakdown in the careful control of polder sluice gates and of irrigation) leads to greater salinity at Amtali and Dacope. At Gosaba, which is the saltiest location to start with, it has less of an impact. Climate change is projected to increase or decrease rainfall, and this in turn leads to modelled increases or decreases in runoff from the polders, and thence to decreases or increases in salt concentrations in the soil and ponds and canals. Thus, the main impacts of climate change are through the indirect impacts on salt concentrations, rather than the direct impacts of the amount of water supplied as rainfall. Management practices to remove salt from polders are therefore likely to be effective in combatting the impacts of projected climate change. Increasing river salinity with sea level rise generally has little impact at Amtali (where the model suggests that not much river water is needed for irrigation) or Gosaba (where the river water is too salty to use even before sea level rise effects).

Publisher:

Nature

Field Of Research:

Agricultural Hydrology (Drainage, Flooding, Irrigation, Quality, etc.)

DOI:

https://doi.org/10.1038/s41598-021-86206-1

Funding Sources:

Funding Body Name	Project/Grant ID
Australian Centre for International Agricultural Research (ACIAR)

Identifier:

EP202155

Publication Sub Type:

Journal article - Refereed

Language:

English

Attribution Statement:

Mainuddin, Mohammed; Karim, Fazlul; Gaydon, Don; Kirby, Mac. Impact of climate change and management strategies on water and salt balance of the polders and islands in the Ganges delta. Scientific Reports. 2021; 11(7041 Full paper):15. https://doi.org/10.1038/s41598-021-86206-1