Observed Water Quality Data Research Articles

Development of a water quality index based on a European classification scheme

This study comprised the development of a new index called the 'universal water quality index (UWQI)'. This index has advantages over pre-existing indices by reflecting the appropriateness of water for specific use, e.g. drinking water supply rather than general supply, and has been developed by studying the supranational standard, i.e. the European Community Standard. Three classification schemes for water quality are proposed for surface water quality assessment. Water quality determinants of the new index are cadmium, cyanide, mercury, selenium, arsenic, fluoride, nitrate-nitrogen, dissolved oxygen, biochemical oxygen demand, total phosphorus, pH and total coliform. The mathematical equations to transform the actual concentration values into quality indices have been formulated. The weighted sum method was proposed to obtain overall index scores based on individual index (sub-index) values. The application of the new index was demonstrated at a sampling station on Tahtali Reservoir in Turkey based on observed water quality data. Results revealed that the overall quality of the surface water falls under the 'excellent' class. On the other hand water quality was strongly affected by agricultural and domestic uses. This technique is believed to assist decision makers in reporting the state of the water quality, as well as investigating spatial and temporal changes. It is also useful to determine the level of acceptability for the individual parameter by referring to the concentration ranges defined in the proposed classification scheme.

Assessing BMP effectiveness: multiprocedure analysis of observed water quality data

Observed water quality data obtained from eight stream monitoring locations within Richland-Chambers Watershed in north central Texas were analyzed for trends using box-and-whisker plots, exceedance probability plots, and linear and Mann-Kendall statistical methods. Total suspended solids decreased at seven out of eight stations, and at two of these stations, the decrease was significant. Mixed results were obtained for nitrogen across the stations. A nonsignificant and significant increase in nitrite plus nitrate nitrogen (nitrite+nitrate N) was noticed in two stations each, whereas at the other four stations showed nonsignificant decrease. The results of organic nitrogen (Org N) was similar to nitrite+nitrate N except that the two stations that showed significant increase in nitrite+nitrate N showed nonsignificant decrease in Org N. Mixed results were also noticed for orthophosphorus (Ortho P) including nonsignificant decrease at two stations, significant decrease and increase at one station each, and nonsignificant increase in four stations. In general, total phosphorus (TP) decreased at all stations, significantly at some, except one station where it increased significantly. Decreasing trends in sediment, Org N, Ortho P, and TP were likely related to implementation of best management practices (BMPs). Increasing trends in dissolved constituents including Ortho P and nitrite+nitrate N were likely due to increased surface residue as a result of some BMPs such as conservation tillage.

Nutrients/food chain model for Lake Zapotlan (Mexico)

A nutrients/food chain model was developed considering the linkage between water balance and energy balance models for Lake Zapotlan. Lake Zapotlan is located in the southern part of Jalisco State, Mexico, and is classified as a warm, tropical water body, endorheic, very shallow, and highly eutrophic. Kinetic parameters were calibrated using previously reported values in the literature for other lakes. The model simulates the concentration of eight state variables for the lake: algae, herbivore and carnivore zooplankton, nitrates, ammonium, SRP, DOC and POC. A set of eight simultaneous ordinary differential equations (ODE) were generated, assuming an initial set of conditions considering the existing hydrologic and water quality information of the streams flowing into the lake. The ODE system was solved and calibrated by using observed water quality data of the lake. In this way, we have estimated the internal fluxes of nutrients and dissolved oxygen in the lake and their interaction with the food chain.

A STUDY ON FORMATION PROCESS AND ESTIMATION METHOD OF WATER QUALITY HYDROGRAPH IN A SMALL BASIN

The purpose of the present study is to clarify formation process of the water quality hydrograph. Generation function in formation process of water quality hydrograph is estimated from observed water quality concentration, discharge and rainfall data using our method proposed in this paper. From the results of analysis, generation function is expressed as rainfall intensity and initial water quality concentration function. Water quality hydrograph is rationally and simply estimated using this function and the estimation method is applied to several water quality hydrograph. The result of calculation is match well with the observed water quality data. It can be concluded that the proposed lumped analysis method can express water quality hydrograph in a small basin effectively and simply.

Characterization of Fate and Transport of Isoxaflutole, a Soil-Applied Corn Herbicide, in Surface Water Using a Watershed Model

The objective of this study is to conduct a comprehensive assessment of the transport of isoxaflutole and RPA 202248 and their accumulation potential in semistatic water bodies, using a distributed watershed scale model and observed water quality data. A conceptual model was developed to characterize the fate and transport of isoxaflutole residues to and in surface water. The soil and water assessment tool (SWAT), a continuous daily time-step watershed model, was used to simulate the processes identified in the conceptual model. Monitoring data were available for a number of surface water bodies within the major product use area as a result of extensive and intensive residue monitoring. Detailed product use information at the zip-code level was obtained through dealer sales and a grower survey. The hydrologic and chemical transport results from the SWAT model were validated by comparison to available monitoring data from selected water bodies. Upon validation, the model was used to simulate the fate of isoxaflutole-derived residues in the water bodies using long-term historical weather data. The results from this investigation indicate no evidence of long-term accumulation of isoxaflutole and its metabolite RPA 202248 in semistatic water bodies.

AN ANALYSIS OF EFFECTS OF AQUATIC MACROPHYTES ON WATER QUALITY IN A SHALLOW MARSH

Aquatic macrophytes function in several ways in aquatic environment. We have analyzed the effects of aquatic macrophytes focusing on the reduction of resuspension of bottom sediments. Aquatic macrophytes are known to suppress the development of wind wave in shallow waters. Reduced wave height leads to the reduction of the resuspension of bottom sediments. This function that aquatic macrophytes may have seem important in deciding the water quality of shallow water bodies. A numerical simulation model was developed to estimate the quantitative effects of aquatic macrophytes on the water quality of a shallow marsh. Simulation results showed good agreement with observed water quality data. A simulation case that assumed dense vegetation of which area was maximum in recent years resulted in less turbid and lower organic matter concentration. The degree of reduction in suspended solids presumed by the simulation agreed well with the previous records in Inba marsh, Chiba prefecture that experienced the decay of aquatic macrophytes. Restoration of native aquatic macrophytes is important to restore the marsh to a previous clear state.

Scaling issues relating to phosphorus transfer from land to water in agricultural catchments

Various scales of input data exist to parameterise diffuse pollution models for the UK. For screening methodologies such as the phosphorus indicators tool—PIT [Heathwaite, A.L., Sharpley, A.N., Bechmann, M., 2003a. The conceptual basis for a decision support framework to assess the risk of phosphorus loss at the field scale across Europe. Journal of Plant Nutrition and Soil Science 166, 1–12; Heathwaite, A.L., Burke, S., Quinn, P.F., 2003b. The nutrient export risk matrix (the NERM) for strategic application of biosolids to agricultural land. International Association for Hydrological Sciences Publication 285, 1–9], which is applied throughout England and Wales, some assessment of the implications of using input data derived at different scales must be made. This work is further driven by practical issues such as licensing costs and data availability, which mean that not all data are readily accessible for all end users. This paper represents a first step towards quantifying the ‘value-added’ to model predictions by using input data derived at three different scales: 50×50 m, 1×1 km and 5×5 km. Model runs using PIT were carried out against observed phosphorus water quality data from the River Start and River Gara, which are the main sub-catchments of Slapton Ley, a grade 1 National Nature Reserve in southwest England. Model runs for the main 46 km 2 Slapton catchment were also undertaken. The results show that some improvement in the ability of the model to capture the observed water quality behaviour may be made by using higher resolution DEM data, though these improvements may be outweighed by the extra data processing and computational time. Conversely, model runs driven by the 5 km data demonstrate consistent under-prediction for all three test catchments, which is perhaps not surprising given the greater degree of averaging underlying datasets at this scale. Results from the 1 km datasets provide the best agreement with observed water quality data, and appear to provide the ‘best available’ means of parameterising PIT at the national scale.

Uncertainty Analysis of Pesticide Residues in Drinking Water Risk Assessment

ABSTRACT Pesticide residues in drinking water can vary significantly from day to day. However, water quality monitoring performed under the Safe Drinking Water Act (SDWA) at most community water systems (CWSs) is typically limited to four data points per year over a few years. Due to this limited sampling, likely maximum residues may be underestimated in risk assessment. In this work, a statistical methodology is proposed to study two types of uncertainties in observed samples and their propagated effect in risk estimates. The methodology was demonstrated using data from 16 CWSs that have three independent databases of atrazine residue to estimate the uncertainty of risk in infants and children. The results showed that in 85% of the CWSs, chronic risks predicted with the proposed approach may be two- to four-folds higher than that predicted with the current approach, wheras intermediate risks may be two- to three-folds higher in 50% of the CWSs. In 12% of the CWSs, however, the proposed methodology showed a lower intermediate risk. A closed-form solution of propagated uncertainty was developed to demonstrate the number of years (seasons) of data and sampling frequency needed to reduce the uncertainty of risk estimates. In general, this methodology provided good insight into the importance of addressing uncertainty of observed water quality data and the need to predict likely maximum residues in risk assessment.

Development of an overall index of pollution for surface water based on a general classification scheme in Indian context.

Various National and International Agencies involved in water quality assessment and pollution control have defined water quality criteria for different uses of water considering different indicator parameters. Classification schemes for water quality criteria/standards developed by these agencies differ in addition to terminologies used such as Action level, Guide level etc. in defining the concentration values in these classes. In the present article a general classification scheme viz. Excellent, Acceptable, Slightly Polluted, Polluted and Heavily Polluted water is proposed for surface water quality assessment. The concentration ranges in these classes are defined in Indian scenario considering Indian Standards and CPCB criteria. Standards by the European Community (EC), WHO etc. and the reported facts about the pollution effects of important water quality indicator parameters on the surrounding were also taken into account. The mathematical equations to transform the actual concentration values into pollution indices are formulated and corresponding value function curves are plotted. Based on the individual index values, an 'Overall Index of Pollution' (OIP) is estimated. The application of OIP is demonstrated at a few sampling stations on river Yamuna based on observed water quality data. The general classification scheme along with concentration ranges defined in these classes will be of immense use for determining the surface water quality status with reference to specific individual parameter, and the OIP for assessing the overall water quality status in Indian context.