Study area: The Chalan Beel is situated at 24.35°–24.70°N and 89.10°–89.35°E. Historically, Chalan Beel was spread over the Upazilas (Sub-districts) of the districts of Rajshahi (Paba, Bagmara and Mohonpur), Pabna (Chatmohor, Bhangura and Faridpur), Sirajgong (Tarash, Ullapara, Raigonj, and Shahjadpur), Natore (Sadar, Singra, Gurudaspur, and Baraigram), Naogoan (Manda, Raninagar, and Atrai) and Bogra (Nandigram). However, presently the beel has been squeezed and now lies only in the districts of Pabna, Sirajgonj, and Natore due to crisscross roads, embankments, and other infra structural development. Therefore, the research was conducted in three representative cluster sites in the above districts. At the experimental site, three cluster sites covering a river, a canal, and a beel were selected for this study. The cluster sites were the Gumani and its adjacent floodplain as (CS 1 : the Gumani) under Natore, the Katagang and its adjacent floodplain as (CS 2 : the Katagang) under Sirajgong and the Baral, and its adjacent floodplain as (CS 3 : the Baral) under Pabna where the sampling for CAS and FES were performed. The water and sediment samples were collected from these sites and quality parameters wereanalyzed. GIS mapping was carried out covering all the areas. Sample collection: Water and soil samples were collected monthly. Samples were taken from three places and were mixed to make one sample with three replicates for each cluster site over one year. On the sampling date, some parameters were measured in the fi eld and other parameters samples were measured in the laboratory of the Faculty of Fisheries (FoF), BAU and in the Soil Resource Development Institute (SRDI) regional office, Dhaka. The sediments were analyzed in four major seasons, namely in the months of August, October, January, and April. The physico-chemical parameters of water such as surface water temperature, transparency, depth, pH, conductivity, total dissolved solids (TDS), total alkalinity (TA), nitrate nitrogen (nitrate-N), phosphate phosphorus (phosphate-P) and ammonia nitrogen (NH3 -N) were monitored monthly. The sediment properties included pH, organic matter (%), total nitrogen (%), available phosphorous (available-P) and exchangeable potassium (exchangeable-K). On each sampling date, water samples were collected from three sites with three replicates and were stored in clean white plastic bottles. One hundred ml of water samples from each of the bottles were filtered through 47-μm glass fiber paper (Whatman GF/C) and were acidifi ed (pH≤2) for nutrient analysis. The beel sediment samples were collected for laboratory analysis at the time of water sample collection from the cluster sites at each season at 0–15 cm depth. The samples were then air-dried at room temperature and the stones, gravel, plant roots, leaves etc. were picked up and removed, and then ground and sieved through a 20-μm size sieve. Finally, these samples were preserved in polythene bags for laboratory analysis. Methods for water and sediment analysis: Surface water temperature was recorded using a thermometer. Transparency was measured by a standard Secchi disc of 25 cm diameter and water depth was measured by graduated bamboo pole fixing to the bottom soil in every sampling spot. The water pH value was determined by a digital pH meter (Model-HANNA-HI-9142) and pH of the sediment was measured by a glass electrode pH meter using sediment: water suspension ratio of 1:2.5. Conductivity and total dissolved solids (TDS) were measured through a conductivity meter (JENWAY Model 4200). Surface water temperature, transparency, water depth, pH, conductivity, total dissolved solids (TDS) were recorded on the spot in the sampling sites. Determination of nitrate-N (NO3 -N), phosphate-P
(PO4 -P) and ammonia nitrogen (NH3 -N) were performed on filtered neutral samples (pH≤7) by a Hach kit (DR/2010 Spectrophotometer) in the water quality laboratory, Bangladesh Agricultural University, Mymensingh. Total alkalinity was determined in the same laboratory. The percent organic carbon of sediment was determined volumetrically by wet oxidation methods. Total nitrogen of sediment was estimated by Micro-Kjeldahl method. Available-P was extracted from the sediment by shaking 0.5 mol/L NaHCO3 solution (pH 8.5). Exchangeable-K was estimated with the help of flame photometer. Statistical analysis: For statistical analysis of water and sediment quality parameters, one-way analysis of variance (ANOVA) was performed and also compared in a repeated measure ANOVA. If the main effect was found significant, the ANOVA was followed by Duncan’s Multiple Range Test (DMRT) to compare the variations among the treatments means. All statistical tests were carried out at a 5% significance level using SPSS software.