Regional Cooperation in Flood Management in the Ganges-Brahmaputra-Meghna Region: Bangladesh Perspective

Bangladesh is known to behighly vulnerable to floods. Frequent floods have put enormous constraints on its development potential. Unfortunately, the frequency of high intensity floods is on the rise. So far the country has struggled to put a sizeable infrastructure in place to prevent flooding in may parts of the country with limited success. In recent times, it was found that losses of lives and valuable assets could be significantly minimized by implementing non-structural measures including the improvement of flood forecasting and warning system. The existing flood forecasting and warning capacity of Bangladesh could be more effective if real-timedata could be acquired from upstreamareas within the Ganges-Brahmaputra-Meghna (GBM) catchment, where runoff is generated. In order to do so, Bangladesh needs to foster an effective regional cooperationwith the other GBM regional countries of India, Nepal, and Bhutan. This article examines how GBM regional cooperation could be useful towards managing floods in Bangladesh in particularand the region in general.     

The Disastrous Flood of 1998 and Long Term Mitigation Strategies for Dhaka City

The disastrous flood of 1998 was a result of excessiverainfall all over the catchment areas of the major rivers of Bangladesh. Dhaka City, which is surroundedby rivers on all sides, was seriously affected despite the completion of Phase I of the Dhaka IntegratedFlood Protection Project (DIFPP). Water entered into the protected part of the city throughhydraulic leakage such as buried sewerage pipes, breached and incomplete floodwalls, ungated culverts andinoperative regulators. The drainage network and retention ponds of the city were found to be in poorconditions and capacities of the pumping stations were found inadequate. There was a serious lack of coordinationbetween the agencies responsible for flood protection and drainage of the city. These issues must beaddressed to achieve long-term flood mitigation. In addition, feedback from both the experts andgeneral public indicated that completion of Phase II of DIFPP was essential to bring the eastern part ofthe city under flood protection. Other structural measures suggested in this paper include installing andmaintaining adequate drainage and pumping capacity and timely operation of regulators. This studyalso suggests a set of non-structural measures for flood mitigation that include protectingthe retention ponds, raising public awareness on maintaining the city drains, introducing landzoning and flood proofing in the eastern part of Dhaka, and stream lining institutional bottlenecks.     

Carbohydrates in humic and fulvic acids from sediments of Suo sound, Japan

Vertical distributions of carbohydrates in humic and fulvic acids isolated from coastal sediments in Suo sound were investigated by gas chromatography and Sephadex gel chromatography. Humate carbohydrates were composed of fulvic acid carbohydrates (70 to 95%). Apparent molecular weight distribution of fulvic acid carbohydrates in vertical direction of sediments was 3·5 to 7·4% below molecular weight (M.W.) 1000, 32 to 42% for M.W. 1000 to 5000, 7·4 to 24% for M.W. 5000 to 10 000, 11·5 to 15·5% for M.W. 10 000 to 25 000, and 28 to 34% for M.W. over 25 000, respectively. Humic acid carbohydrates are present in high molecular weight over 25 000. Fulvic acid carbohydrates decreased with increasing depth. A decrease of humate carbohydrates occurred between the surface layers to 20 cm depth, below 20 cm vertical change of carbohydrates was not observed.     

Dynamics of carbohydrates in the Norwegian Sea inferred from monthly profiles collected during 3 years at 66°N, 2°E

Water samples were collected monthly for 3 years at 66°N, 2°E in the Norwegian Sea, 250 nautical miles off the Norwegian coast. Concentrations of mono- and polysaccharides were measured with the 2,4,6-tripyridyl-s-triazine (TPTZ) spectroscopic method. Total dissolved carbohydrates varied from 3.4 to 28.2 μM C of all samples and the ratio of carbohydrate to dissolved organic C (DOC) varied from an average of 14% at 0–25 m depth to 11% at 800–2000 m depth. This indicates that dissolved carbohydrates were a significant constituent of DOC in the Norwegian Sea. Polysaccharides varied from 0.4 to 21.5 μM C and monosaccharides from 0.7 to 11.7 μM C at all depths. The level of monosaccharides was relatively constant at 2.8–3.2 μM C below the euphotic zone, whereas polysaccharides showed more varying concentrations. Dissolved carbohydrates accumulated during the productive season, reaching maximum concentrations during summer although interannual differences were observed. A significant positive correlation between Chl a and soluble carbohydrate was found in one growing season with nutrient analyses. Average values for total carbohydrates were highest in the surface – 0 to 25 m – with 13.3 μM C and decreased to 8.4 μM C at 800–2000 m depth. The ratio of monosaccharides to polysaccharides exhibited a marked seasonal variation, increased from January to a maximum in June of 1.1, and declined to 0.5 in July.     

管线系统抗震性能研究方法综述

现代公共建筑非结构构件的投资比远远大于结构构件的建造成本比例,非结构构件在地震中的破坏会造成巨大经济损失。作为一种典型的非结构构件,管线系统的破坏往往导致建筑丧失给水、排水以及消防等多重使用功能。从拟静力试验、动力试验、振动台试验、数值模拟及易损性分析等角度对管线系统抗震性能研究方法进行了系统总结,介绍各类研究方法的应用实例及其利弊,并对管线系统抗震性能研究方法的发展方向进行了展望。     

Vertical changes of POC flux and indicators of early degradation of organic matter in the South China Sea

Tie-series sediment trap materials at different water depths and surface sediments in northern and central South China Sea (SCS) were analyzed for organic carbon, amino acids, amino sugars and carbohydrates. Results show that particulate organic carbon (POC) is mainly derived from marine plankton, only 1.4%–1.6% of primary production sinks into deep SCS water column and less than 0.22 % of primary production ultimately reaches the sediments. The ranineralization and dissolution of organic matter as well as the compositional alterations of organic matter mixtures may mainly take place in the upper few hundred meters of water column, deep carbonate (opal) lysocline zones, and interface layers between sediments and water column, rather than in mid-waters. The organic geochemical parameters such as (T ^aa +T ^sug )OC%, AA/AS, Gluam/Galam, Arom. AA/non-prot. AA, ASP/b-ALA, Glu/g-ABA decrease from living marine plankton (or planktonic shells), to settling particulate matter and to sediments suggesting that they appear to be gad early degraded indicators of organic matter. Project supported by the National Natural Science Foundation of China (Grant No. 49776297). Cruises financially supported by State Oceanic Administration and German Federal Ministry of Research and Technology.     

Enzyme activities in the water column and in shallow permeable sediments from the northeastern Gulf of Mexico

The activities of extracellular enzymes that initiate the microbial remineralization of high molecular weight organic matter were investigated in the water column and sandy surface sediments at two sites in the northeastern Gulf of Mexico. Six fluorescently labeled polysaccharides were hydrolyzed rapidly in the water column as well as in permeable sediments. This result contrasts with previous studies carried out in environments dominated by fine-grained muds, in which the spectrum of enzymes active in the water column is quite limited compared to that of the underlying sediments. Extracts of Spirulina, Isochrysis, and Thalassiosira were also used to measure hydrolysis rates in water from one of the sites. Rates of hydrolysis of the three plankton extracts were comparable to those of the purified polysaccharides. The broad spectrum and rapid rates of hydrolysis observed in the water column at both sites in the northeastern Gulf of Mexico may be due to the permeable nature of the sediments. Fluid flux through the sediments is sufficiently high that the entire 1.5 m deep water column could filter though the sediments on timescales of a few days to two weeks. Movement of water through sediments may also transport dissolved enzymes from the sediment into the water column, enhancing the spectrum as well as the rate of water column enzymatic activities. Such interaction between the sediments and water column would permit water column microbial communities to access high molecular weight substrates that might otherwise remain unavailable as substrates.     

Chemical characterization and composition of dissolved organic matter in Jiaozhou Bay

Biologically utilizable dissolved organic compounds, including dissolved organic carbon (DOC), dissolved carbohydrates (DCHO) and dissolved free amino acids (DFAA) were analyzed in filtered surface seawater samples collected at 19 stations in Jiaozhou Bay, China, on June 3, 2007. In these samples, concentrations of DOC, dissolved free carbohydrates (DFCHO), dissolved combined carbohydrates (DCCHO), total dissolved carbohydrates (TDCHO) and total dissolved free amino acids (TDFAA) ranged from 141.7 to 191.1 μmol C/L, 1.98 to 18.18 μmol C/L, 5.04 to 24.90 μmol C/L, 14.52 to 30.36 μmol C/L, and 1.83 to 11.89 μmol C/L, respectively. As a major component of the dissolved carbohydrates, the concentrations of DCCHO were about three times higher than those of DFCHO. Three major constituents of the DFAA were threonine (23.0±5.7 mol%), glutamic acid (16.6±3.2 mol%) and arginine (9.1±3.3 mol%). Based on the composition of DFAA, a molar C:N ratio of 3.60±0.75 in DFAA was derived, indicating longer carbon chains in the amino acids. DCCHO (8.1%) was the most abundant fraction of DOM in most samples, followed by DFCHO (4.8%) and TDFAA (2.7%). These DOM concentrations displayed a decreasing trend from the coast to the central region. Significant correlations were found between the DCCHO and DFCHO concentrations (r=-0.724, n=19, P<0.001) and the DCCHO and TDCHO concentrations (r=0.506, n=19, P=0.027).     

Bacterial production,glucosidase activity and particle-associated carbohydrates in Dona Paula bay,west coast of India

Size-fractionated bacterial production, abundance and α- and β- glucosidase enzyme activities were studied with respect to changes in hydrography, total suspended matter (TSM), chlorophyll a, particulate organic carbon and nitrogen ratio (POC:PON), 1.5 M NaCl-soluble and 10 mM EDTA-soluble carbohydrates (Sal-PCHO and CPCHO) and transparent exopolymeric particles (TEP) in the surface waters from July 1999–2000 at a shallow coastal station in Dona Paula Bay, west coast of India. The bulk of the total bacterial production and glucosidase activity were associated with particles (75% and >80%, respectively). Total bacterial production was linearly correlated to chlorophyll a (r = 0.513; p < 0.05) whereas enzyme activity was significantly correlated to TSM (α-glucosidase: r = 0.721 (p < 0.001); β-glucosidase: r = 0.596 (p < 0.01)). Both α-glucosidase (r = 0.514; p < 0.05) and β-glucosidase enzymes (r = 0.598; p < 0.01) appeared to be involved in the degradation of CPCHO and Sal-PCHO, respectively. Changes in α-glucosidase/β-glucosidase ratios highlighted the varying composition of particulate organic matter. The bacterial uptake of ¹⁴C-labeled bacterial extracellular carbohydrate measured over 11 days showed a strong linear correlation between ¹⁴C-uptake and bacterial production using tritiated thymidine. The turnover rate of ¹⁴C-labeled carbohydrate-C was 0.52 d⁻¹, higher than the estimated annual mean potential carbohydrate carbon turnover rate of 0.33 ± 0.2 d⁻¹. Our study suggests that carbohydrates derived from sediments may serve as an important alternative carbon source sustaining the bacterial carbon demand in the surface waters of Dona Paula Bay.