Hydrology: Current Research

This paper compares the results produced by MODFLOW, a constant-density model, to results produced by SEAWAT, a variable-density model, to investigate the feasibility of using MODFLOW in a saline environment below an estuary known as the Indian River Lagoon. The comparison was conducted over sixteen numerical simulation cases at different conditions of estuarine salinity CL, hydraulic conductivity anisotropy ratio Kr, and water table elevations on the freshwater boundaries in a two-dimensional vertical domain. The use of MODFLOW at the study site under the calibrated Kr distribution ranging from 1000-20,000 was found to accurately match the field-measured and SEAWATsimulated results with a remarkable increase in accuracy at higher groundwater elevations. The study determined a critical value of Kr of 1000 above which, MODFLOW simulations of the variable-density problem produced results that agreed well with those produced by SEAWAT. However, MODFLOW starts to produce significant errors with Kr below the critical value and hence, it should not be used for simulating variable-density environments when Kr<1000. The amount of submarine groundwater discharge (SGD) predicted by either model, and also MODFLOW accuracy in predicting the SGD are directly proportional to the head difference between the groundwater divide elevation and the lagoon water surface, but to a lower extent, are inversely proportional to CL.

This paper compares the results produced by MODFLOW, a constant-density model, to results produced by SEAWAT, a variable-density model, to investigate the feasibility of using MODFLOW in a saline environment below an estuary known as the Indian River Lagoon. The comparison was conducted over sixteen numerical simulation cases at different conditions of estuarine salinity CL, hydraulic conductivity anisotropy ratio Kr, and water table elevations on the freshwater boundaries in a two-dimensional vertical domain. The use of MODFLOW at the study site under the calibrated Kr distribution ranging from 1000-20,000 was found to accurately match the field-measured and SEAWATsimulated results with a remarkable increase in accuracy at higher groundwater elevations. The study determined a critical value of Kr of 1000 above which, MODFLOW simulations of the variable-density problem produced results that agreed well with those produced by SEAWAT. However, MODFLOW starts to produce significant errors with Kr below the critical value and hence, it should not be used for simulating variable-density environments when Kr<1000. The amount of submarine groundwater discharge (SGD) predicted by either model, and also MODFLOW accuracy in predicting the SGD are directly proportional to the head difference between the groundwater divide elevation and the lagoon water surface, but to a lower extent, are inversely proportional to CL.

Water is a major source of microbes, including pathogens that can cause critical pathological conditions and outbreak of epidemics. Due to lack of proper medical waste-management system in Peshawar, most of the waste is disposed of near sewage lines which run parallel to drinking water supply increasing the chances of water contamination. This study was undertaken to examine bacterial and viral pathogens in fresh and waste water in major Health care units. Conventional culturing techniques were used to identify bacterial pathogens followed by biochemical analysis, whereas viral pathogens were detected by Polymerase Chain Reaction (PCR). Analysis of sewage and drinking water supply in major health care facilities of Peshawar city indicated that Klebsiella pneumoniae and Staphylococcus aureus were found in all water samples whereas serious health risk causing bacteria including Mycobactirium tuberculosis were also detected in some regions. Two viral pathogens, Hepatitis C virus (HCV) and Hepatitis B virus (HBV) were found in open sewage water of Khyber Teaching Hospital and Dabgari Garden (G). The presence of these pathogens in water is a serious threat to public health and the environment and calls for immediate action to enforce proper medical waste-management to eliminate the risks to human health.

A geochemical and isotopic techniques were undertaken to characterize groundwater in Northeast Tunisia. Hydrogeochemical investigations demonstrated that groundwater can be classified into different water facies. The Ras Djebel-RafRaf aquifer showed a (Ca-Cl-SO4) and (Na-Cl-NO3) water type. Data inferred from 18O and deuterium isotopes in groundwater samples indicated recharge with modern rainfall. Water characterized by lower δ18O and δ2H values is interpreted as recharged by non-evaporated rainfall originating from Mediterranean air masses from Mediterranean air masses at higher altitude. However, water with relatively enriched δ18O and δ2H contents is thought to reflect the occurrence of an evaporation process related to the long-term practice of flood irrigation.

In this study, three different sensors of satellites including the Moderate Resolution Imaging Spectroradiometer (MODIS), Multi-angle Imaging Spectroradiometer (MISR), and Total Ozone Mapping Spectrometer (TOMS) were used to study spatial and temporal variations of aerosols over ten populated cities in Iran. Also, the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model was used for analyzing the origins of air masses and their trajectory in the area. An increasing trend in Aerosol concentration was observed in the most studied cities in Iran during 1979-2016. The cities in western part of Iran had the highest annual mean of aerosol concentration. The highest AOD value (0.76 ± 0.51) was recorded in May 2012 over Ahvaz, and lowest value (0.035 ± 0.27) was recorded in December 2013 over Tabriz. After Ahvaz, the highest AOD value was found over Tehran (annual mean: 0.11 ± 0.20). The results show that AOD increases with increasing industrial activities, but the increased frequency of aerosols due to land degradation and desertification is more powerful in Iran. The trajectories analysis by the HYSPLIT model showed that the air masses come from Egypt, Syria, and Lebanon, and passed over the Iraq and then reached to Iran during summer. Aerosol Radiative Forcing (ARF) has been analyzed for Zanjan (AERONET site) during 2010-2013. The ARF at surface and top of the atmosphere were found to be ranging from -79 wm-2 to -10 Wm-2 (average: -33.45 Wm-2) and -25 wm-2 to 6 wm-2 (average: -12.80 Wm-2), respectively.

Smallholder farmers in Ethiopia generally face widespread problems driven by climate change. For this reason, the study of climate change at watershed level might be critical to solve the problem from its root. The study was conducted in Lake Haramaya Watershed, Eastern Ethiopia to project ad characterize the climatic condition of the coming thirty years (2020-2050). Thirty-four years of rainfall, maximum and minimum temperature baseline data were collected from National Meteorological Agency of Ethiopia. Whereas, thirty years (2020-2050) projected rainfall, maximum and minimum temperatures were downscaled from MarkSim web version for IPCC AR5 data (CMIP5) using five climate models namely: BCC-CSM1-1, CSIRO-Mk3-6-0, HadGEM2-ES, MIROC-ESM, MIROCESM- CHEM, and MIROC5 under two Representative Concentration Pathways (RCPs): RCP4.5 and RCP8.5. The results of the study revealed that the annual mean rainfall will be increased by 20.70 and 24.14% under RCP4.5 and RCP8.5, respectively compared to baseline average value of 777.51 mm/yr. The annual rainfall under RCP4.5 ranges from 769.6 to 1090 mm/yr having the CV value of about 11%; whereas, under RCP8.5, it will range from 771.9 to 1129 mm/yr with the CV value of 13.17%. Kiremt (JJAS) season rainfall will increase from the baseline of 107.55 mm/yr to 135.79 and 136.27 mm/yr under RCP4.5 and RCP8.5, respectively. Moreover, a study indicated that the annual and seasonal temperature under RCP4.5 and RCP8.5 will be expected to increase during 2020-2050 period. Under high emission scenario of RCP8.5, the annual maximum temperature could rise from 24.73°C baseline to 25.41°C.

Ethiopia will be more vulnerable to climate change. Because of the less flexibility to adjust the economic structure and being largely dependent on agriculture, the impact of climate change has far reaching implication in Ethiopia. Simulation models of watershed hydrology and water quality are extensively used for water resources planning and management. The study aims to Simulate Hydro Climatological impacts caused by Climate Change: the case of Hare Watershed, Southern Rift Valley of Ethiopia. In the study the daily data values of rainfall and discharge for the current period of 1980-2006 were used. Historical Representative Concentration Pathway (RCPs) data of precipitation and temperature were used to extract raw climate variables. The raw RCPs data were corrected using a bias correction method. The downscaled climate data such as, RCP4.5 and RCP8.5 scenarios was used for the future period assessment. Soil water assessment tool (SWAT) models were used to Simulate Hydro Climatological impacts caused by Climate Change. Calibration and validation of the model output were performed by comparing predicted streamflow with corresponding measurements from the Hare river outlet for the periods 1991-2002 for calibration and 2003-2006 for validation. The models’ calibration results show a good agreement with the observed flow with the coefficient of determination is 0.85 and a Nash Sutcliffe efficiency is 0.73. The result of mean monthly percentage changes of climate variables from the baseline period were used to simulate future projections of stream flow. Stream flow projections for future time periods showed that mean monthly stream flow may increase by 12.2, 8.0, and 13.9% at 2020s, 2050s, and 2080s, respectively, from the baseline period for RCP4.5 scenario, whereas for RCP8.5 scenario, it will be expected to increase by 7.3, 13.4, and 15.4% for 2020s, 2040s, and 2080s, respectively. The model simulations considered only future climate change scenarios assuming all spatial data constant. But change in land use scenarios other climate variables will also contribute some impacts on future stream flow.

Contaminant removal may largely be a function of many microbial processes in constructed wetlands. However, the role of microbial diversity for the removal of swine waste in constructed wetlands is limited. Here, we used 454/ GS-FLX pyrosequencing to assess archaeal, bacterial, and fungal composition within a surface flow constructed wetland to determine their spatial dynamics and contaminant removal within the wetland. We analyzed our data using UniFrac and principal coordinate analysis (PCoA) to compare community structure and specific functional groups of bacteria, archaea, and fungi in different sections of the wetland. PCoA analysis showed that, bacterial, archaeal, and fungal composition were significantly different (p=0.001) for the influent compared to the final effluent. Our results showed that, the wetland system contained relatively higher proportions of bacteria and fungi than archaea. Most of the bacteria and archaea that were associated with nitrogen removal were affiliated with Nitrosomonas which are ammonia oxidizing bacteria (AOB), Candidatus Solibacter, an anaerobic ammonia oxidizing bacteria (Anammox), as well as Nitrosopumilus, ammonia oxidizing archaea (AOA). The detection of AOB, Anammox, and AOA in this wetland shows abundance and diversity of these microorganisms that are responsible for nitrification processes in constructed wetlands.

The two main transport mechanisms that occur simultaneously under unstable flow conditions are transport of saltwater from an overlying salt source to the porous media, and transport of salt through the porous media. These mechanisms were simultaneously studied through two fixed mass experiments conducted over 15 days. The transport through the porous media was also studied via three continuous injection experiments lasting between 5 to 29 days. There was no hydraulic gradient across the porous media in any of the experiments. Experiments were conducted in a 1 cm thick plexiglass rectangular sand column (1.70 m × 0.61 m × 0.61 m). The saline source concentration was 36 g/l, and the source heights were 4.5 cm. The sand porosity and hydraulic conductivity were 32% and 9.0 m/d, respectively. The rate of mass transport from the source to the porous media was observed by measuring the salt concentration within the source, while the salt transport through the porous media was documented by measuring breakthrough curves at five locations within the sand column. Fixed mass experiment results, using mass analysis, showed that the salt transport from the source to the porous media was deterministic since both experiments produced identical rates of mass transport from the source to the porous media, the salt transport through the porous media was stochastic since the observed breakthrough curves at the five locations were considerably different. The breakthrough curves measured in three identical continuous injection experiments were also very different supporting the results of the fixed mass experiments. The implications of these findings are that, under unstable conditions, one can predict the salt mass that would enter from a salt source into the underlying porous media with certainty, one cannot predict the rate or pattern of salt transport through the porous media itself.