The paper intends to provide guidance to evaluate and identify a standard ground water chemistry data for irrigation in south western region of Bangladesh. During the course of hydrogeological studies in the study area, twenty water samples were collected from twenty different villages and chemically analyzed. The analytical results revealed that the water was slightly acidic to slightly alkaline (pH 6.68 -7.32) and TDS values range from 565 to 1073 mg/l. The other parameters like sodium adsorption ratio, (SAR) (0.10 -0.27), sodium percentage (3.22 -7.13), residual sodium carbonate, (RSC) (3.2 -5.33) and potential soil salinity, (PS) (less than 30) were below the desired limit suggesting the suitability for irrigation purpose. Considering SAR, permeability index and salinity hazard, all waters could be applied safely for irrigation without any hazard to crops.
Key words: Ground water, irrigation, water chemistry, south-west Bangladesh
IntroductionIrrigation is an age-old art. Historically, civilization has followed the development of irrigation. The duration of civilized people is probably dependent on many factors, of which a permanent profitable agriculture is significantly important (Hansen et al. 1979). Around 80% people in Bangladesh are living in rural areas (BBS 2001) and are belonging to agrarian structure. Food security of that inhabitant is mainly agro based. The agriculture sector plays a pivotal role in the economy of the country accounting for 31.6 per cent of total GDP in [2000][2001]. The agricultural sector comprises of crops, forests, fisheries and livestock. Of the agricultural GDP, the crops sub-sector contributes to 71 per cent itself. Keshabpur Upazila (Fig. 1) belongs to mature deltaic plain (Choudhury 2001). More especially this area is a part of Gopalganj-Khulna peat basin. Differences in elevation between river banks and basin centre usually are about one meter (Brammer 1997). During the time that the delta was being built, the activity of the river Ganges helped to build it up latter as a plain (Abedin et al. 1990). Kopothaksha is the main river * Corresponding author: . 1 channel in the region. But due to Farrakka Barrage at the upstream, the natural flow of the river is being shut down day by day. This accelerates the siltation at the river. As a result of acute water shortage in the dry season, awful drainage congestion and overflowing in the monsoon are the common feature in the study area. Fig.1. Location map of the study area (Source: Banglapedia).In the Keshabpur Upazila (Fig.1), total irrigable land area are 194 sq. km, among it 163 sq. km are at present in irrigated condition. The irrigation system of this area was totally based on ground water. For the irrigation purpose total five thousand and five Chemical suitability of ground water for irrigation 123 hundred shallow (80 m) tube-wells were established in the Keshabpur Upazila. The study area, Trimohini union consist four hundred ninety five and Sagardari union consisted of si...