Development and Integration of Sub-hourly Rainfall–Runoff Modeling Capability Within a Watershed Model

Increasing urbanization changes runoff patterns to be flashy and instantaneous with decreased base flow. A model with the ability to simulate sub-daily rainfall–runoff processes and continuous simulation capability is required to realistically capture the long-term flow and water quality trends in watersheds that are experiencing urbanization. Soil and Water Assessment Tool (SWAT) has been widely used in hydrologic and nonpoint sources modeling. However, its subdaily modeling capability is limited to hourly flow simulation. This paper presents the development and testing of a sub-hourly rainfall–runoff model in SWAT. SWAT algorithms for infiltration, surface runoff, flow routing, impoundments, and lagging of surface runoff have been modified to allow flow simulations with a sub-hourly time interval as small as one minute. Evapotranspiration, soil water contents, base flow, and lateral flow are estimated on a daily basis and distributed equally for each time step. The sub-hourly routines were tested on a 1.9 km² watershed (70% undeveloped) near Lost Creek in Austin Texas USA. Sensitivity analysis shows that channel flow parameters are more sensitive in sub-hourly simulations (Δt = 15 min) while base flow parameters are more important in daily simulations (Δt = 1 day). A case study shows that the sub-hourly SWAT model reasonably reproduces stream flow hydrograph under multiple storm events. Calibrated stream flow for 1 year period with 15 min simulation (R ² = 0.93) shows better performance compared to daily simulation for the same period (R ² = 0.72). A statistical analysis shows that the improvement in the model performance with sub-hourly time interval is mostly due to the improvement in predicting high flows. The sub-hourly version of SWAT is a promising tool for hydrology and non-point source pollution assessment studies, although more development on water quality modeling is still needed.     

Firms’ willingness to invest in a water fund to improve water-related ecosystem services in the Lake Naivasha basin,Kenya

A valuation scenario was designed using a contingent-valuation approach and presented to decision makers in business firms in Kenya’s Lake Naivasha basin to test how applicable a water fund might be as a potential financing mechanism for a payment for water-related ecosystem services scheme. The findings indicate that measuring a firm’s willingness to invest in ecosystem services could help determine whether a firm would invest and engage with other stakeholders to pool their investments in ecosystem services. Linking the institutional decision-making behaviour of a firm and its willingness to invest in a water fund is the novelty of this article.     

Is water scarcity a constraint to feeding Asia's growing population?

Growing population and wealth, as measured by per capita GDP, are predicted to put water resources and food production in Asia under increasing pressure over the next few decades. Critical factors include the increasing demand for animal proteins in diets and the growing need for energy. Climate change impacts may further reduce available water resources because of greater evaporation losses in some areas and storms and floods in others. If we are to overcome these significant constraints on food production, we must turn to strategies that are focused around sustainable intensification of agriculture. These include modernization of old irrigation schemes to increase water productivity, innovative concepts that capture and store flood runoff for use in agriculture, much more recycling and reuse of urban wastewater, and other efficiency-improvement techniques. However, these will not happen in a policy vacuum, and it is argued that reforms are needed in water policy, water training and water management institutions across Asia.     

Watershed Prioritization Using Saaty’s AHP Based Decision Support for Soil Conservation Measures

The identification of environmentally stressed areas for planning soil conservation measures requires an efficient decision support tool to provide appropriate weights for various topographical, morphological, climatological and management factors responsible for soil erosion. In the present study, Saaty’s analytical hierarchy process (SAHP) with nine erosion hazards parameters (EHPs) including soil loss (SL), sediment yield (SY), sediment production rate (SPR), sediment transport index (STI), slope (Slp), Drainage density (D _d ), channel frequency (C_f), form factor (R _f ), circulatory ratio (R _c ) has been used as a decision support system for identification of environmentally stressed sub-watersheds in Benisagar dam catchment of Bundelkhand region (Madhya Pradesh, India). The SAHP is a structured technique for dealing with complex decisions which involves building a hierarchy of decision elements, making comparisons between each possible pair in each cluster, provides weighting for each element within a cluster and checking the consistency of the decision based on a consistency ratio. The Benisagar dam catchment having excessive erosion due to undulating topography, limitation of soil depth and absence of conservation measures affects reservoir storages due to silting problems. For prioritization purposes, the Benisagar dam catchment has been divided in to 36 sub-watersheds with their areas ranging from 0.77 to 6.53 km² and all nine EHPs for various sub-watersheds have been computed. The pair wise comparison matrix and final weights for all the EHPs have been determined using SAHP with the acceptable limit of consistency ratio. The final priority ranks for sub-watersheds have been computed by summing the multiplication of SAHP weights and their corresponding normalized values of EHPs. From the analysis, it has been observed that eight sub-watersheds covering 20.15 km² and seven sub-watersheds covering 19.41 km² areas fall under very high and high priority respectively.     

Adsorption study of a commonly used antidepressant drug, fluoxetine hydrochloride, onto a crosslinked β-cyclodextrin-carboxymethylcellulose polymer

A study was carried out by ultraviolet-visible (UV-vis) and Fourier transform infrared (FTIR) spectroscopies to establish the efficiency of adsorption of fluoxetine hydrochloride (FLU), onto a crosslinked β-cyclodextrin-carboxymethylcellulose (β-CD-CMC) polymer. The adsorption was performed in mixtures containing aqueous FLU solution at 20 mg/L and 0.01-0.30 g of the β-CD-CMC polymer, at 25 °C, and atmospheric pressure under stirring. The results have revealed that the adsorption is a rapid process and the polymer possesses a high affinity for FLU with an adsorption capacity of 5.076 mg of FLU/g of polymer. This adsorption may involve the formation of a stable inclusion compound β-CD-CMC/FLU through the penetration of the FLU aromatic ring (A and/or B) into the β-CD cavity, and a physical adsorption with the polymer network. The inclusion compound can be stabilized by the formation of H-bonds between the -CF(3) group of FLU and the 6'-OH group of β-CD, and van der Waals interactions between the FLU aromatic ring and β-CD cavity. The data from a kinetic study have also indicated that the adsorption process was well described by the pseudo-second-order kinetic model, in which the initial adsorption rate and constant were estimated at 1.938 mg/g min and 0.075 g/mg min, respectively. Moreover, the results of adsorption equilibrium fitted the Freundlich isotherm, indicating a multilayer coverage and heterogeneous surface. Together, these results suggest that the adsorption of FLU onto the crosslinked β-CD-CMC polymer could constitute an advantageous technology for removing this commonly used antidepressant drug from wastewater due to the high adsorption capacity of the polymer and non-toxic character of β-CD to humans and environment.     

Capillary effect on the sloshing of a fluid in a rectangular tank submitted to sinusoidal vertical dynamical excitation

Surface tension effects on fluid sloshing in a tank subjected to external excitation has been less studied. This work aims at understanding this phenomenon in order to derive practical solutions to problems faced in several engineering. A tank containing a fluid with a free surface is submitted to gravity and capillary forces and subject to external dynamic excitation. Introduction of vertical sinusoidal dynamical excitation leads to a problem of paramtric oscillations governed by the Mathieu equation. Analysis of the Mathieu equation shows the existence of stable and unstable regions in the stability diagram. Some results induced by harmonic excitations on the fluid sloshing are presented. When the external dynamical excitation amplitude ~ is small, periodic solutions appear in stable regions and when e increases, the fluid behavior is not perfectly periodic and the amplitudes are not regular. Nonlinear effects make the behavior of the fluid complicated and render it almost unpredictable. In stable regions, the solution remains bounded at any time. When changing the perturbation parameter 6, the phase difference increases and also with the increase of the surface tension.     

Use of a stable carbon isotope to assess the efficiency of a drinking water treatment method with CO?

CO? gas with a special isotopic signature (δ13C = -35.2‰ vs. VPDB) was used as a marker to evaluate the efficiency of a drinking water treatment method and the effect of an ultrasonic (US) stirrer. This treatment was developed to prevent precipitation and corrosion effects in water-supply systems. The research work was performed using a laboratory-scale pilot plant that was filled with tap water. The stable isotope analyses of δ13C-DIC (Dissolved Inorganic Carbon) in the water samples indicated that the maximum content of added CO? gas in DIC was in the range of 35 to 45%. The use of the US stirrer during the entire experiment decreased the method's overall efficiency by 10%, due to degassing at a late stage of the experiment but accelerated the dissolution process in the early experimental stage.     

Water Allocation as a Planning Tool to Minimise Water Use Conflicts in the Upper Ewaso Ng’iro North Basin, Kenya

Inadequate water resources management and a general decline in rainfall have aggravated water scarcity problems in the Upper Ewaso Ng’iro North Basin in Kenya. Furthermore, water use conflicts in the basin have escalated in recent decades due to increased competition for available water resources. Excessive abstraction of the declining river water mainly for irrigation in the Mount Kenya and Nyandarua foot zones often leads to reduced water flow during the dry seasons, greatly affecting downstream water users. Increased water use in the basin coupled with deterioration of the vegetative cover has resulted in reduced water flows in the Ewaso Ng’iro river and its major tributaries. In addition, lack of sufficient knowledge about available water resources and current lack of coordination in water resources management in the basin often result in water deficits which have hampered development in the downstream catchment. The goal of this study was to match the water requirements of various competing sectors in the basin with the available water resources in order to attain both economic and ecological sustainability. To achieve this, GIS techniques were used to quantify the spatial and temporal stream flow. The Water Evaluation and Planning (WEAP) model was applied to evaluate water resources development based on an equilibrium scenario of the current water demand. Water use was simulated for five different sectors (domestic, livestock, wildlife, irrigation and reserve). The analyses revealed that high water demand for irrigation was the main cause of excessive water abstraction particularly in the upstream catchments, giving rise to water shortages and consequently, water use conflicts downstream. The study, therefore, recommends that rainwater harvesting be promoted in the basin in order to improve water availability for productive use.     

Homotopy-based analytical approximation to nonlinear short-crested waves in a fluid of finite depth

A nonlinear short-crested wave system, consisting of two progressive waves propagating at an oblique angle to each other in a fluid of finite depth, is investigated by means of an analytical approach named the homotopy analysis method(HAM). Highly convergent series solutions are explicitly derived for the velocity potential and the surface wave elevation. We find that, at every value of water depth, there is little difference between the kinetic energy and the potential energy for nonlinear waves. The nonlinear short-crested waves with a larger angle of incidence always contain the more potential wave energy. With the aid of the HAM, we obtain the dispersion relation for nonlinear short-crested waves. Furthermore, it is shown that the wave elevation tends to be smoothened at the crest and be sharpened at the trough as the water depth increases, and the wave pressure crests and troughs become steeper with increasing incident wave steepness.     

Local Markets for Payments for Environmental Services: Can Small Rural Communities Self-Finance Watershed Protection?

Payment for environmental service (PES) programs are innovative approaches for watershed and natural resources management that increasingly are being used around the world. Most well-studied PES examples rely predominately, if not entirely, on large governmental and outside non-governmental organizations for financial and management assistance. We examine the potential for using a locally-financed PES scheme in a small, agricultural community in a developing country as a means to preserve environmental services of watersheds, namely clean drinking water. A dichotomous choice, contingent valuation survey is used to examine the community??s demand for protection of the headwaters of the nearby river, the source of their drinking water. The survey results demonstrate local water users?? substantial willingness to pay for increased protection of the watershed environmental services. We find that a local-market PES scheme for watershed services, even in a relatively low-income context, may be sufficient to protect ecosystem services independent of external financial resources.     

Clean development mechanism: a way to sustainable waste management in developing countries?

The Clean Development Mechanism established under the Kyoto Protocol allows investors in the developed world to invest in the developing world in return for emission credits. The CDM has two goals—to contribute to the reduction of emissions in the developed countries, and to promote sustainable development in the developing country. The objective of this paper is to analyze the project portfolio of 400 published CDM projects in the sector “waste handling and disposal” according to their project and technology characteristics.     

Particle counting as a tool to predict filterability in membrane bioreactors activated sludge?

Activated sludge quality is one of the major factors influencing flux decline in membrane bioreactors (MBRS). Sludge filterability is a recognized parameter to characterize the physical properties of activated sludge. Decrease in filterability is linked to a higher number of submicron particles. In our present research we studied whether particle counting techniques can be used to indicate deflocculation of the sludge suspended fraction to submicron particles, causing the aforementioned filterability decrease. A total number of 105 activated sludge samples were collected in four full scale municipal MBRS. Samples were tested for filterability and particle counting in the range 2-100 microm. In 88% of the membrane tank samples the filterability varied between good and poor, characterized by the deltaR20, being 0 < deltaR20 < 1. Filterability varied following the season of the year, stability of the MBR operation and recirculation ratio. The membrane tank filterability can be improved by applying low recirculation ratio between MBR tanks. The applied particle counting methodology generated reproducible and reliable results in the range 10-100 microm. Results show that differences in filterability cannot be explained by variations in particle size distribution in the range 10-100 microm. However, measurable deflocculation might be masked by the large numbers of particles present. Therefore, we cannot exclude the suspended particles as a possible source of submicron particles that are subsequently responsible for MBR sludge filterability deterioration.     

The role of groundwater in loading of nutrients to a restricted bay in a Precambrian Shield lake Part 2. – Numerical modeling

Previous modeling of hydrologic and nutrient budgets of lakes in Precambrian Shield regions have generally ignored groundwater as a source of water and supplier or sink of nutrients. This paper and its companion (Part 1) address this science gap by probing the role of groundwater in the nutrient balance for a restricted bay of a Precambrian Shield lake (Lake of the Woods) that experienced extensive shoreline development in the 1990s. Based on field data (Part 1), we applied a 3D reactive transport model (FEFLOW) to simulate the fate of nutrients in a cottage septic plume in groundwater and seepage into the bay. Corresponding simulations are for chloride and septic tracers in the plume, and 1D modeling of the mass balance of one septic tracer (acesulfame) in the bay. Our results suggest that, before they reach the lake, significant portions of the septic plume contaminants are attenuated by various processes, including uptake by transpiring plants. Extrapolating, we estimate that, for annual fluxes to the bay, groundwater seepage contributes ~1–3% of the phosphorus (P) and ~2–5% of the dissolved inorganic nitrogen (DIN). The results suggest that these groundwater nutrient fluxes to the bay are derived mainly from natural background sources. In contrast, cottage septic plumes contribute a quarter of the groundwater flux of DIN to Poplar Bay, while the septic contribution of P to the bay is negligible. We estimate that the largest sources of P and DIN fluxes to Poplar Bay are influx from the open lake and atmospheric deposition.     

The Afghan water law: “a legal solution foreign to reality”? 1

In this article the suggested permit and licence systems included in the draft Afghan Water Law of 2008 (superseding those laws of 1981 and 1991) are examined by comparing them with main canal data from two pilot studies within the Kunduz Basin. The comparison highlights the difficulty of making these proposed legal frameworks operative. Overall, it appears that the sections within the law on permits and licences are not implementable within or even useful for the traditional irrigation systems, but mainly play into the hands of the national hydrocracy and please international donors.     

Is Shallow Water a Suitable Surrogate for Assessing Efforts to Address Pallid Sturgeon Population Declines?

It is hypothesized that slow, shallow water habitats benefit larval pallid sturgeon Scaphirhynchus albus; however, testing this hypothesis is difficult, given the low number of larval pallid sturgeon present in large rivers. In contrast, relatively large numbers of age‐0 shovelnose sturgeon Scaphirhynchus platorynchus have been sampled, providing a potentially useful baseline to assess the importance of slow, shallow water to age‐0 sturgeon of both species (hereafter age‐0 sturgeon) in the lower Missouri River. Thus, we investigated the potential relationships between the prevalence of shallow water <1.5 m and the age‐0 sturgeon catch rates at multiple scales. Age‐0 sturgeon were usually sampled in water >1.5 m, and catch rates were usually highest in the upper half [i.e. river kilometre (RKM) 400 to 800] of the lower Missouri River study area, whereas the availability of water <1.5 m was usually highest in the lower half (i.e. RKM 0 to 400). Similarly, there was no relationship between age‐0 sturgeon mean catch‐per‐unit effort and ha/km of water <1.5 m at any studied scale. Our results may suggest that shallow water, as currently defined, may not be a suitable surrogate for assessing efforts to address pallid sturgeon population declines. However, it is still unknown if lack of appropriate habitat is currently limiting pallid sturgeon. Published 2015. This article is a U.S. Government work and is in the public domain in the USA. River Research and Applications published by John Wiley & Sons Ltd.     

HEC—5Q Model Applied to a Lake System in Illinois for Water Quality Evaluations

Abstract

The United States Army Corps of Engineers HEC-5Q model was applied to Lake Spring-field and two proposed lakes (Hunter Lake and Lick Creek Reservoir) to be built for supplementing Lake Springfield's water. Lake Springfield is the water supply reservoir for the city of Springfield, Illinois. Water from the lake is also used for cooling the city's power plant complex. The model was calibrated and verified on Lake Springfield using monitored data in 1986 and 1988. Eight water quality constituents were simulated. Calibration, verification, and predictions were made only for temperature, dissolved oxygen, nitrate-nitrogen, and phosphate-phosphorus. The calibrated and verified model was used to predict water surface elevations and constituent concentrations in the three lakes, individually and in combination, with meteorological and estimated flow data for a twenty-month period in 1953–1954, the most severe drought of record. The model provided a useful tool in the water quality evaluations of the three lakes.     

Nexus meets crisis: a review of conflict,natural resources and the humanitarian response in Darfur with reference to the water–energy–food nexus

Darfur has been widely used as a case study by both those arguing for causality between environmental scarcity and war and those disputing it. This article challenges that approach by drawing on debates taking place within Darfur, reflecting on both the conflict and the humanitarian response. It argues that reviewing Darfur on its own terms makes a stronger basis to identify transferable lessons for interventions elsewhere. It considers water, food and energy, and finds that supporting governance is an essential theme for promoting economic recovery and laying a foundation for a well-managed water–energy–food nexus.     

Application of Froude dynamic similitude in anaerobic baffled reactors to prediction of hydrodynamic characteristics of a prototype reactor using a model reactor

An anaerobic baffled reactor is a system developed in recent decades and has been used as part of the treatment of high-strength wastewater. Since the function of this system is based on its hydrodynamic features, hydrodynamics and the regime of the flow through the reactor are crucial. In this study, a prototype reactor with eight chambers, which had a total volume of 48 L, and a model reactor, whose dimensions were half of those of the prototype reactor, were used. The Froude dynamic similitude in these reactors was investigated. The results show that the curve dimensionless variances were 0.089 and 0.096 for the prototype and model reactors, respectively, the short-circuiting indices were 0.483 and 0.489 for the prototype and model reactors, respectively, the effective volume and short-circuiting index measurement errors were both 1%, the hydraulic efficiency error was 2%, and the Peclet and dispersion number errors were both 7%. Most of the compared indices were close to one another in value. Therefore, the model reactor can be used based on the Froude dynamic similitude to determine hydrodynamic characteristics of a baffled reactor at a full scale.     

Tributary contributions to sediment deposited in the Jacuí Delta,Southern Brazil

The Jacuí Delta drains into Lake Guaíba which is the main source of water for more than two million people in South Brazil and has suffered from pollution with heavy metals and phosphorus. The objective of the current research is to demonstrate how the use of sediment source tracing techniques, in combination with sediment flux monitoring, can improve understanding of the sediment source contributions to one of the largest lakes in South America. The sediment flux monitoring results were based on data obtained from 12-years of records of water flow and suspended sediment concentrations. The sediment source fingerprinting approach was based on the use of geochemical tracers. Based on the study, the respective contributions of the tributaries to the sediment in Lake Guaíba were estimated to be as follows: the Jacuí River (median of 54% - interquartile range (IQR) 34–71%), the Caí River (12%, IQR 7–16%), the Sinos River (5%, IQR 1–20%), and the Gravataí River (16%, IQR 10–30%). These results are similar to those derived from the sediment flux monitoring, namely: the Jacuí River (70%), the Caí River (19%), the Gravataí River (4%), and the Sinos River (7%). These results demonstrate that the sediment source fingerprinting approach combined with sediment flux monitoring can provide a useful means of estimating the respective sediment contributions from individual tributaries in large and complex delta systems and may provide a powerful tool to guide water resource management.     

The Compensation Mechanism and Water Quality Impacts of Agriculture-Urban Water Transfers: A Case Study in China’s Chaobai Watershed

Water transfer from agriculture to urban uses will likely become increasingly common worldwide. The objectives of this study were to evaluate the effects of converting paddy rice to dry land crops (PPRDC) on local farmers’ income in China’s Chaobai watershed and to analyze the responses of surface water quality to the change in cropping system. An on-site investigation of 485 households and water quality data from 1999 to 2008 are presented in this study. The cost of cultivation as a percentage of the total revenue was 22.3 % for rice and 30.1 % for corn, and the calculated compensation level (CCOM) should be 6172.3 Yuan?ha^?1. PPRDC provided farms with stable income without regard to drought and flood: thus, farmers responded positively to PPRDC, and 76.7 % of farmers expected to continue PPRDC. Inflow water quality was improved in terms of total nitrogen (TN) and nitrate (NO₃–N) because of the reduction in fertilizer and pesticides after PPRDC, but there was no significant change in total phosphorus (TP). PPRDC not only reallocates water resource to different users but also improves water quality through crop adjustment. A dynamic compensation mechanism based on changing crop price is required for the future water transfer project.