Aquifer Salinity and its Suitability for Irrigation in the Southwest Coastal Region of Bangladesh
MUKTARUN ISLAM, PhD Research Assistant, IWFM, BUET INDIA WATER WEEK 2013, “Efficient Water Management: Challenges and Opportunities” S-6: Agricultural Water Use 8-12 April, 2013 Vigyan Bhawan, New Delhi
Introduction
Salt water intrusion limits the groundwater availability from coastal aquifers in many regions of the world
The coastal region of Bangladesh is experiencing similar problems
The current study focuses on the saline and non-saline aquifer domain identification and evaluation of the degree of salinity in the identified aquifer domains in the southwest coastal region of Bangladesh
The irrigation suitability of the aquifers has been also evaluated
Study Area Situated
in the southwest coastal area of Bangladesh Located
at between latitude 23015′N and 22055′N and longitude 89024′E and 89036′E Temperature Mean The
varies from 25.80C to 35.80C
annual Rainfall: 1781mm
region is significantly influenced by tidal effects
Materials and Methods
The investigation of groundwater salinity distribution are analyzed based on literature, secondary and the primary data
The presence of salinity in depth are evaluated from the analysis of the geophysical log and time series salinity data collected from the secondary sources
New bore logs are installed to generate the salinity distribution with the aquifer depth to supplement the secondary data
Soil and water sampling are done to identify the presence of salinity
Identification of saline layers from bore log samples
Identification based on salinity concentration: Setting monitoring Wells
The aquifer where water contains the concentration of ≤2dS/m is considered as a nonsaline aquifer and when it exceeds 2dS/m, the aquifer is considered as the saline aquifer.
Irrigation water suitability
EC: Salinity limit: <3.0 dS/m (Rahman and Ravens croft, 2003 and BRRI, 2001) For rice 2dS/m may be applied SAR limit: 12-18 Range of pH: 6.5 to 8.5
Evaluation of EC at Kalia and Tularampur The minimum concentration in saline aquifer domain in Kalia was observed as 3.31 dS/m and the maximum was over 5.15 dS/m.
The minimum concentration in saline aquifer domain in Tularampur was observed as little over 3.4 dS/m and the maximum was 5.38 dS/m.
In both the location the variation of salinity concentration in non-saline aquifer domain is very small.
Evaluation of SAR SAR =
Na + Ca + + + Mg + + 2
ď ś SAR values are ranged between 12.47 to 3.83 supports that the groundwater is free from any sodium hazard and supporting the highly suitability for irrigation
Evaluation of pH ď ś
The pH value of water samples for two sites are found to vary from 7.75 to 8.08 with an average of 7.97
ď ś
Thus pH values in the area are found excellent for crop production
Conclusions
In the southwest region of Bangladesh, the saline aquifer layer is found underlain by non-saline aquifer in one location and overlain by non-saline aquifer in another location.
pH value is found excellent for crop production
SAR values are also supports that the groundwater is free from any sodium hazard and is highly suitable for irrigation
Due to the presence of saline layers the aquifer can not be fully developed although the aquifer has been found potential from the hydro-geologic settings
So it is required to develop both saline and non-saline aquifer domains conjunctively for augmentation of usable water supply by developing appropriate technology
Thank You