Water quality management: case studies

Hydrological Sciences-Bulleiin-des

Sciences Hydologiques, 24, 2, 6/1979

SESSION IX

Water quality management: case studies A S I T K. B I S W A S International Institute for Applied Systems Analysis, A-2361 Laxenburg, Austria; and Director, Biswas and Associates, 3 Valley View Road, Ottawa, Canada Papers reviewed (all published in IAHSPublication no. 125) 1. Z. Adamczyk, J. Grêla, R. Konieczny and H. Slota, A simple mathematical model of quantitative and qualitative processes occurring in the stream channel for water distribution control. 2. A. B. Birtles and S. R. A. Brown, Computer prediction of the changes in river quality regimes following large scale inter-basin transfers. 3. W. J. Grenney and B. Finney, Water resources management using integer programming models. 4. B. Hock, Water quality modelling as a tool for decision making in Hungary. 5. T. D. Steele, Assessment techniques for modelling water quality in a river basin impacted by coal resource development.

Of the five papers presented, three discuss problems in Europe—Poland, UK and Hungary—and two are from the USA. The framework used for this General Report is in two parts. The first part provides a summary and comments on each individual report, and the second half consists of comments on the topic as a whole. The first paper by Adamczyk, Grela, Konieczny and Slota deals with the utilization of potential water resources of the Upper Vistula basin by developing a simulation model of quantitative and qualitative characteristics of the River Vistula between Pustynia and Niepolomice stations. It is divided into two subsytems depending on the type and scope of management problems involved. The first one, a multi-reservoir subsystem, is a standard water distribution system, where quality problems are not serious, and thus need not be analysed vigorously. Water quality, on the other hand, is a serious problem in the River Vistula due to heavy utilization of its water. The optimization techniques used for establishing water distribution rules for the multi-reservoir subsystem is not discussed in the paper. Some of the results obtained from this simulation model, however, are used for the Vistula subsystem model, which is based on the classical Streeter-Phelps equation. The model is capable of handling the following pollutants: BOD, DO, oxygen consumption, phenols, chlorides, sulphates and suspended solids. Waste discharges were described by mean values of data obtained over three years. Model validation procedures with regard to both water quantity and quality are discussed. The authors conclude that even though it was not possible to construct a detailed model due to 'insufficient or incompatible' data, simple models should be developed. Further information from the authors on the following points will be useful. (1) Only 'significant' inputs to and outputs from the system were included. With regard to water quality, what levels were considered 'significant'? (2) One of the fundamental assumptions was that the time delays within the system 171

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were disregarded. Some information on the validity of such an assumption will be helpful, especially now that the modelling effort is complete. (3) Since the self-purification process was neglected, could it not have introduced significant errors in the model results? (4) Waste discharges were described by mean values over three years. Many industrial processes produce wastes that vary with regard to both quantity and quality, even diurnally. Thus, some information on types of industrial wastes considered will be useful for a better understanding of the system being modelled. (5) What is being done with the model at present? Is it being used for operational, planning or decision-making processes? If so, some further information will be useful. The paper by Births and Brown is on computer prediction on changes in river water quality regimes due to interregional transfers, an alternative that is now being increasingly considered in many countries (Golubev & Biswas, 1978; Midgley, 1978). The paper discusses the possibility of meeting future water demands in the Thames Water Authority area by water transfers at appropriate times from the River Severn, whose flows could be supported, if necessary, from surface storages in Wales. Since the water qualities of the two systems differ, the following potential problems were identified for the Thames area: (i) descaling, pitting, corrosion in distribution networks; (ii) adverse effects on existing water treatment works; (iii) changes in the biological balance of the storage reservoirs; and (iv) deleterious effects on the life processes of invertebrate animals and fish. The objective of the study was to quantify the new quality regimes by simulation, and to have pertinent information available to answer questions pertaining to the chemical, ecological and economic problems. The models of the three rivers, Severn, Avon and Thames, were developed along identical techniques, based on analyses of the river hydrographs into distinct components: sewage effluent returns, two or three aquifer discharge components and a surface runoff component. The various component concentrations were estimated by using a nonlinear least squares parameter estimation technique, and net river concentrations were synthesized by summing the mass loads of each component. Simple autoregressive models were used to remove any systematic variance. Chloride, orthophosphate and nitrogen concentrations have only been discussed in the paper. The General Rapporteur would like to raise the following points. (1) In view of the fact that the results have been presented to facilitate estimation of two factors, one of which is the adverse effects of the interbasin transfer on organisms, an explanation of the rationale for choosing and limiting studies only to the quality determinands mentioned earlier will be helpful. This is because other pollutants like trace metals, pesticides, or even temperature, could have significant impacts on ecosystems. (2) The authors have correctly pointed out that 'from an environmental viewpoint, it is unlikely that the extent or even the possibility of disruptions to the balance of existing ecosystems can be quantified on the basis of such condensed data and simple criteria'. Another important factor,however, is the combined and/or synergistic effects of different pollutants on ecosystems. Are there any plans to consider such factors in the present study? (3) A major problem encountered in many countries for interbasin transfers has been the public attitude to and perceptions of such an alternative (Biswas, 1978a). Has there been any study conducted in this area, and if so, what are the results?

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The paper by Grenney and Finney is on mixed integer programming models. The authors point out that water quality management models developed so far primarily deal with only one stream parameter (DO) and minimize treatment costs in terms of removing only BOD. The model response is static since only one set of technical coefficients is used to relate waste constituent removal to stream quality changes, and thus interactions are not taken into account. By linking pollution loading and stream quality response with a nonlinear simulation model, which provides the constraints for an integer treatment cost minimization mathematical programme, the authors develop a technique for handling pollution loads and water quality parameters. The simulation-optimization model developed was used to carry out a sensitivity analysis and also for the Jordan River in Utah. In addition to DO, the authors considered phosphorous, BOD, ammonia, nitrate and algae. The authors also provide some interesting information like the running time and cost of the programme. The following questions arise from this paper. (1) The optimal treatment scheme for the 1995 flows was the same as for the 1975 flows. Since this is normally unusual, could the authors provide an explanation for this solution? (2) The increased load from expected growth was assumed to be uniform over all the point loads. This is also an unusual situation. Are there any special reasons for such an assumption? (3) What is the present status of the models developed? Are these being used for planning and/or decision-making purposes? The paper by Hock is on the development of a water quality management programme for the Sajd catchment area, which is the most important basic material producing region for heavy industry in Hungary. The two pollution characteristics considered were COD represented by the dichromate value of oxygen consumption and ammonium-ion, NH4. After verification, it is expected that the model will be used to analyse water quality conditions until 1985. The objective function of the optimization task was the net annual cost expressed as the sum of capital investment, OMR costs and the cost of administration. The results of optimization have been shown in terms of COD, NHj and COD plus NH4. The investment costs required for their implementation have also been indicated. The results indicated that the economic costs of optimal strategies for NH4 and COD plus NHj were significantly higher than the COD-based optimization. An attempt was also made to predict water quality conditions for the Hungarian side of the River Sajd. This indicates that only the values obtained by the optimization of COD plus NHÎ will satisfy the stream standards by the year 1985. Some clarification from the author will be useful on the following points. (1) It has been mentioned in several places that '53 sewage and waste water treatment technologies have been developed for the 17 pollution sources'. The General Rapporteur had some problem in understanding what is exactly meant by '53 treatment technologies'. (2) In the earlier part of the paper, it was mentioned that the major industrial productions in the Sajd basin consisted of coal and iron ore mining; production of steel, nitrogen fertilizer, ethylene, polyethylene, caprolactane and PVC and electric

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power generation. Under these conditions, how realistic is it to limit water quality parameters to only two, COD and NH4? (3) In the study, an implicit assumption seems to be that the chemical and biochemical interactions between water quality components can be neglected. Would the author comment on the validity of this assumption? The last paper of this session is an evaluation of direct and indirect impacts of coal and associated economic development on the regional water resources of the Yampa River basin in the United States. Currently, the predominant consumptive use of water in the basin is for irrigation and stock watering. Seven potential coal development alternatives have, however, been identified. Environmental stresses that may develop due to residual generation and higher water-use implications of each alternative are currently being evaluated. Depending on the alternative selected, the total gross output by 1990 might increase from 76 to 292 per cent more that the 1975 base, and population may increase from 89 to 196 per cent. Five modelling approaches were considered: waste load assimilative capacity, travel time and reaeration characteristics, reservoir-modelling analysis, sediment appraisal and groundwater solute transport. The results of the five component studies were used to integrate the forecasts of water use and generated residuals into each study design and analysis of development alternatives. Significant results of each study component have been highlighted in the paper. Obviously, due to length constraints, the author was not able to provide more information on how the integration of the various modelling techniques was carried out. The General Rapporteur believes that such integrations are absolutely essential for appropriate regional planning and development and would urge the author to provide more information on how the integration process was carried out. G E N E R A L COMMENTS

Planning and implementing appropriate water quality management is a complex and time-consuming process, and alternative designs, when available, are generally discrete rather than continuous. The designs are often based on limited data, and naturally there is a great deal of uncertainty when one attempts to predict the future on the basis of limited data and understanding. Furthermore, it is implicitly assumed that the recent past is also the key to the future, at least so far as the design life period is concerned. It is time that we seriously debate the validity of this assumption for many reasons. First is the climate itself, which has never been stable or constant through the earth's past history, and there is absolutely no reason to believe that the situation will alter in the future. Thus, a changing climate is an established fact, and continuation of the natural long-term variability will assure the onset of glaciation at some time in the future. It is highly likely that the next major climatic change, whenever it occurs, may not be recognized until the trend is well established, since with the present state-of-the art, it is not possible to distinguish with any degree of confidence between the onset of persistent change and short-term fluctuations. Thus, even if it is assumed that the global temperature has gone down between 1940 and 1970 (this is debatable) the cooling process has occurred no faster than, and not yet lasted as long as, the warming trend that immediately preceded it.

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So far as water resources planning is concerned, these trends that are minor in terms of the earth's overall climatic history, could be rather important events. The time scale over which such trends occur, and the nature and magnitude of the trends are important parameters to be considered for water resources planning. There seems to be basically two schools of thought concerning the incorporation of climatic fluctuations in water planning. The first school of thought suggests that since the economic life of most water resources structures is between 40 and 100 years, and since there has been no evidence of climatic change during the past 200 years, the probability of a major change during the next 200 years is minimal, and therefore the whole question is somewhat academic. Thus, Chin & Yevjevich (1974) state that 'since most systems have been built with the economic project life in the range of 40-100 years, the chances are minimal that the expected natural water supply would be significantly different during these life spans than in the past 200 years. . . .This question is, however, not crucial for the next several generations of contemporary earth population, but rather is more of an academic interest like many other human concerns with the long-term future.' They further attempted to show that climatic fluctuations could be reduced to a deterministic component based on the Milankovich theory of astronomical cycles and a simple Markovian stochastic component. Several hydrologists and climatologists have taken a contrary view, and have pointed out that climatic variability is unquestionably an established fact. Accordingly, the variability should be recognized, and should be analysed and used in the water resources planning and management process. Mitchell et al. (1975) clearly state that 'The lessons of history seems to be that climatic variability is to be recognized, and dealt with as a fundamental quality of climate, and that it should be potentially perilious for man to assume that the climate of future decades and centuries will be free from similar variability'. The importance of considering climatic variability has been clearly demonstrated, especially in terms of water resources management, by O'Connell & Wallis (1973). They showed that the reservoir firm yield, assuming a 50-year design life, could have different estimates even when Markov and other persistent generating mechanisms used yielded samples having identical expected values for the mean, variance and lagone correlation. In other words, the analysis clearly indicated that it is not only important for hydrologists and water planners to understand the nature of climatic variability and persistence, but also imperative that such considerations be incorporated in the planning process. In another paper, Wallis & O'Connell (1973) showed that statistical analyses of hydrological data of an average period of years would usually lead one to believe that a Markov generating mechanism adequately represents the streamflow pattern in a real world. Such analyses could instill a false sense of security amongst water resources planners, since they are likely to be erroneous. This is because various statistical tests carried out do not have the power to distinguish between samples of such lengths taken from Markovian and more persistent generating mechanisms. Second, and still with climate, the present climate—which is considered to be normal—may not be normal in the longer perspective. Consider the following facts (Bryson & Murray, 1977): (1) since 1880, only half of the decades in the Northern Hemisphere have been as warm as or warmer than 1960-1970; (2) since 1700 A.D., all 30-year periods have been colder than the 1931-1960 period; (3) About 90 per cent of the past million years has been colder than our own time. Bryson and Murray further point out that 'during cooler periods, our analysis of past climates indicates, there is

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greater variability in week-to-week and year-to-year weather'. If this conclusion is correct, it has major implications in terms of water quality management. A common problem in all the papers reviewed, is the lack of data over a long period of time. If the climate of the recent past is not representative, one must question the accuracy of analysing this data to obtain statistical parameters which are then used for the analysis of the future. Third, in many parts of the world the land use patterns are changing rapidly, which often have effects on both the quantity and quality of streamflow. A typical example is the deforestation in the Himalayas which has contributed to the increase in both frequency and magnitude of floods in rivers originating therefrom. These are difficult questions to which we do not have immediate answers. A few scientists are working in these areas, and the present status of research in these areas have been reviewed elsewhere (Biswas, 1978b). What is imporant, however, is that we take cognizance of these problems and attempt to develop techniques, and methodologies which can take them into account appropriately in the future. NOTE

Opinions expressed are those of the author and are not necessarily those of any Institute, Agency or Government he is associated with.

REFERENCES Biswas, Asit K. (1978a) North American water transfers: an overview/. Wat. Supply Management, 2, No. 2, 79-90. Biswas, Asit K. (1978b) Climatic fluctuations and agricultural and water resources planning. Report to Land and Water Development Division, FAO, Rome. Bryson, R.A. & Murray, TJ. (1977) Climates of Hunger. University of Wisconsin Press, Madison. Chin, W.Q. & Yevjevich, V. (1974) Almost-periodic, stochastic process of long-term climatic changes. Hydrology Paper No. 65, Colorado State University, Fort Collins. Golubev, G. & Biswas, Asit K. (1978) Interregional Water Transfers: Problems and Prospects. Pergamon Press, Oxford. Midgley, D.C. (1978) Interregional transfers of water in southern Africa. /. Wat. Supply Management, 2, No. 3, 227-242. Mitchell, S.M., et al. (1975) Variability of the climate of the natural troposphere. Climatic Impact Assessment Program, Monograph 4, Department of Transportation, Washington, D.C. O'Connell, P.E. & Wallis, J.R. (1973) Choice of generating mechanism in synthetic hydrology with inadequate data. In: Design of Water Resources Projects with Inadequate Data (Proceedings of the Madrid Symposium), vol. 1, pp. 377-394: IAHS Publ. No. 108. Wallis, J.R. & O'Connell, P.E. (1973) Firm reservoir yield: how reliable are historic hydrological records. Hydro!. Sci. Bull. 18(3), 347-365.