Hydrology: Current Research

A “real world” study to assess the performance characteristics (precision, accuracy) of the citrate-capped, gold nanoparticle, Ultraviolet-Visible colorimetric method, for quantifying residual poly-diallyl dimethylammonium chloride (poly-DADMAC) in four raw dam and treated potable waters, was undertaken. Using three calibration methods, the method was found to be sensitive (LOQ=2 μg/L), over the linear range 10-30 μg/L. The overall mean within-batch precision (%RSD) was: 7.42 (±7.07) for Method 1, and 7.66 (±7.37) for Method 2; between-batch (reproducibility) (%RSD) was 54.37 ± 30.03) and 35.89 ± 34.89). Statistical data analysis indicated fairly good agreement (no significant difference) for poly-DADMAC levels in 30 samples analyzed by the two methods Method 1 and 2. The residual poly-DADMAC potable water levels (range: <2-8 μg/L), were: on average (±SD) (μg/L), 1.21 (±1.31) for Hazelmere Dam, 1.22 (±0.55) for Midmar Dam, 3.40 ± 3.89) for Inanda Dam, and 3.64 (±3.83) for Nagel Dam. The observed, apparent poly-DADMAC levels, obtained by Method 1, (range: 6-16 μg/L) were, on average (±SD) (μg/L), for the raw water samples: 3.73 (±0.46) for Inanda Dam, 5.73 (±6.57) for Nagle Dam, 6.82 (±9.03) for Hazelmere Dam and 10.12 (±6.94) for Midmar Dam. The study indicated compliance of all treated, potable water for residual poly-DADMAC, to the current international limit of ≤50 μg/L. The relatively high apparent concentration (range: <2-24 μg/L) of poly-DADMAC observed on the raw dam waters was attributed to the presence of Natural Organic Matter (NOM).

The importance of restoring and maintaining environmental flows for sustaining the ecosystem integrity of rivers and estuaries has been recognized and given proper attention in policies and legal frameworks in many countries including Tanzania. The Wami River estuary is small but it plays a vital role in processing riverine nutrients, in trapping sediment, in recycling nutrients in the mangroves, and in supporting the ecology of the Saadani National Park and the livelihood of the local communities. The proper functioning of this estuary to a large extent depends on adequate supply of freshwater flows. Our studies reveal that currently the estuary is ecologically healthy but it is threatened by both increasing sedimentation and declining freshwater flow caused by decreasing rainfall - possibly linked with climate change - and by increasing water demand in the watershed for artisanal and large scale agriculture and irrigation schemes. Environmental flow assessment for the Wami River (with exclusion of estuary) has been done and the minimum flows were recommended. However, like in many other rivers in the country, effective implementation of recommended environmental flows remains to be a challenge. In order to maintain a healthy estuarine ecosystem in the future, it is the obligation of the WRBWO now to stick to and enforce the recommendations of its own environmental flow assessment to regulate water usage in the watershed. A similar recommendation also holds for all other rivers and estuaries in Tanzania.

Sundarbans Estuarine System (SES, 21.25°-22.5° N and 88.25°-89.5° E), comprising the southernmost part of the Indian portion of the Ganga-Bramhaputra delta bordering the Bay of Bengal, is India’s largest monsoonal, macrotidal delta front system. Sundarbans Estuarine Programme (SEP), the first comprehensive observational programme to study tidal as well as salinity features was conducted during 18-21 March, 2011 (Equinoctial spring phase). The main objective of this program was to monitor tides and salinity characteristics within the SES. Out of 30 observation stations, spread over more than 3,600 sq km covering seven inner estuaries, we have chosen river Jagaddal, which is connected with Saptamukhi East Gulley (SEG) in the West and river Thakuran in the East, due to the fact that the station Indrapur situated on this river at location very close to Bay of Bengal represents the condition at the mouth of all seven estuaries. Tidal elevation, salinity, bathymetry and vertical profile of salinity using CTD were measured during the observation period. Observed current data collected from different sources have been used for comparison with computed tidal current. Finally, the estuarine current, bottom drag coefficient and gradient Richardson number have also been computed. Computed values of these parameters have analyzed for interpreting variations for tidal, current and mixing feature prevailing in the estuary.

The present study investigates the potential of soil and soil composites for removal of phenol from solution on a comparative scale. Different experimental parameters were optimized with a novel approach of response surface methodology (RSM) and a central composite design (CCD) for achieving maximum efficiency. Maximum adsorption efficiency (1.44 mg g-1) was obtained at initial pH 5.5, an adsorbent dosage of 7.5 g L-1 and a treatment time of 32.5 mins at a temperature of 313 K as predicted by the RSM design. The phenomenon best fitted the Temkin isotherm at different temperatures. The process was guided by the pseudo-secondorder kinetic model and was analyzed to be spontaneous, endothermic and chemisorption in nature. Characterization of soil particles using Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy showed the changes in its structure and surface morphology both before and after use and explained it’s prospective as a good and environmentally benign adsorbent in very low quantities. Hence, this adsorbent can be implemented as an efficient liner material for the removal of phenol and phenolic compounds from wastewater.

Hydrological models have been used in different River basins across the world for better understanding of the hydrological processes and the water resources availability. It is important to use hydrological model today to assess and predict the water availability of river basins due to climate change to develop a strategies in order to cope up with the changing environment. It is very crucial to properly calibrate and validate models to give confidence to model users in prediction of stream flow. In this study HEC-HMS 3.5 hydrologic model (Developed by US Hydrologic Engineering Center-SMA (with Soil moisture Accounting Algorithm) has been used to calibrate (from 1988-2000) and validate (from 2001-2005) the upper Blue Nile River Basin (Gilgel Abay, Gumera, Ribb and Megech catchment). The model performance tested for each catchment in simulation the runoff flow during calibration and validation period, The Nash-Sutcliff (ENS) and Coefficient of determination (R2) used to evaluate the performance of the model. The results obtained are satisfactory and accepted for simulation of runoff. The deficit and constant loss method, synder unit hydrograph method and exponential recession method, are the best fit performed methods of the hydrological processes of infiltration loss, direct runoff transformation and base flow part respectively. Thus, this study shows that HEC-HMS hydrological model can be used to model the upper Blue Nile River basin catchments for better assessment and prediction of simulation of the hydrological responses. The study recommends further studies which incorporate the land use change of the basin in the model.

This research paper is dealing with Geoelectrical Exploration as a Geophysical method used, Vertical Electrical Sounding (VES) and 2D profile imaging to find a solution of the problems affecting the research station in South of Qantara Skark. This research station is one of the desert research center stations used to develop the desert for agriculture. The area of study is suffering from the shortage of irrigation water whereas, it depends on the water flow of the tributary of Salam Canal which being not available all the time. The appropriate solutions of these problems have been delineated by the results of 1D and 2D geoelectrical measurements. It exhibits the subsurface sedimentary sequences and extension of subsurface layers in horizontal and vertical directions especially in the groundwater aquifer. Moreover, the most suitable locations of drilling water wells could be detected. The surface and subsurface layers of the quaternary deposits consists of sand, sandy clay and clay facies. Nineteen Vertical Electrical Sounding (VES) are arranged as a grid to cover the study area and two 2D geoelectrical imaging profiles are acquired. The results are represented through different contour maps and cross sections that exhibit the horizontal distribution of successive layers which reflect the lithology and changes in all directions. The water bearing layers consisted of two zones. The upper one was less salty than the lower one. The thickness of the upper zone ranges from 5 to 7 meters, but the lower zone ranges between 15 and 30 meters. The last detected layer is clay that decreases in depth towards the Southwest of the study area, causing the phenomenon of water logging. The thickness of the upper zone of the water bearing layer is inadequate for irrigation. Recommended basins to be constructed and filled through nearby drilled wells to overcome this problem. The most suitable location to dig a channel for water drainage is in the Southwest, where there is a less depth to the clay layer and all the layers are dipping toward this side

This case study evaluates a computationally efficient distributed hydrological model, named Coupled Routing and Excess Storage (CREST), for flood modeling of basins in the Connecticut River Basin (CRB). Simulation of discharges is performed by forcing CREST with a long record (eight years) of high resolution radar-rainfall data and potential evapotranspiration maps derived from the North American Regional Reanalysis. The model performance is evaluated against observed streamflows obtained from United States Geological Survey gauging stations at outlet and interior points of various CRB sub-basins. CREST parameters were calibrated based on a three year record (2005-2007) and validated for the remaining data period (2003-2004 and 2008-2009). The model performance evaluation is based on different metrics, including the Nash-Sutchliffe Coefficient of Efficiency (NSCE), Mean Relative Error (MRE), Root Mean Square Error (RMSE), and Pearson Correlation Coefficient (PCC). The analysis shows that CREST slightly underestimated the peak flows, but exhibited a generally good capability in simulating the stream flow variability for the CRB basins. Specifically, NSCE, MRE, RMSE, and PCC values of hourly flow simulations varied from 0.31 to 0.58, -0.06 to 0.13, 61 to 121 (mm) and 0.60 to 0.83, respectively. At daily time scale the performance metrics exhibited improved values indicating that CREST has sufficient accuracy for long term multi-scale hydrologic simulations.

Waterlogging is becoming the major threat to the sustainability of irrigated agricultural lands in Fincha’a Valley Sugar Estate (FVSE). In the present study timely and accurate detection of waterlogged areas through piezometer monitoring and remote sensing indicators, along with their characterization and severity classification has been made. Accordingly, spatial maps of groundwater table (GWT) depth were produced in a Geographic information system (GIS) (ArcGIS 10.2) environment from 40 groundwater monitoring piezometer data. Results of the study revealed that FVSE, after nearly 20-25 years of irrigation, is experiencing a serious waterlogging problem. About 324.4 km2 (75.5%) of the delineated plantation fields are severely waterlogged and 105 km2 (24.5%) are critically waterlogged. The study also revealed that the GWT depth for all selected irrigation fields is very shallow in winter compared to spring, autumn and summer seasons. The seasonal fluctuation and spatial variability of groundwater table in the irrigated fields is owing to excess irrigation water application, nature of the soil, topography and high seepage from water bodies and poor drainage system; hence are the main causes for waterlogging (GWT rise) problem in the study area. The groundwater depth is extremely shallow (<1 m below ground) in most of the piezometer sites (about 94.7% of the study area) throughout the entire season and showed great spatio-seasonal variability. The rate of annual increment of groundwater rise, coupled with seasonal fluctuation, has obvious repercussions and grave consequences for the sustainability of Fincha’a Valley Sugar Estate. The serious problem of the rising groundwater table can be tackled by adopting improved irrigation water management practices, designing drainage system and further geological investigations. Therefore, it is highly suggested to critically study the causes, consequences and solutions of the waterlogging problem (GWT rise) in a concerted and integrated manner to get out of this vicious problem.