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 AreaSituated in the southwest coastal area of Bangladesh

Located at between latitude 23015′N and 22055′N and longitude 89024′E and 89036′E

Temperature varies from 25.80C to 35.80C

Mean annual Rainfall: 1781mm

The 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 non-saline 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 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

2MgCa

NaSAR

Evaluation of pH

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

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