In the 1970's many rivers across industrialised countries were polluted, some to the extent that natural river-life was dramatically impaired and many species simply could not exist in the water. Industrial inputs, including poorly-treated sewage and thermal inputs from power stations, caused some of the more serious problems. Policy-makers in many countries recognised this unsatisfactory state would be best tackled by improving their enforcement of environmental regulation and in some cases improving their legislative framework. Over the years the model of a regulatory environmental protection agency has been widely adopted and these organisations have set about improving river water quality, amongst many other objectives. But how successful has this approach been?
The main objective of regulators with regard to water quality is the protection of endemic flora and fauna, and water quality assessment forms a major part in evaluating how well this is being done. Accordingly, quality assessments across the world focus strongly on chemical and biological criteria. Lists of dangerous chemicals have been drawn up encompassing those substances exhibiting lethal toxicity, severe sub-lethal effects and/or extended environmental persistence, which can in turn lead to harmful bioconcentration. Whilst there are national differences, dangerous substance lists normally contain both metals (mercury, cadmium, zinc, copper, etc.) and organic molecules including a range of organohalogen and organophosphorus pesticides and, more recently, endocrine disrupting chemicals (EDC's). Some regulators divide their dangerous substance lists into most impacting and less severe categories (e.g. European List I and List II Dangerous Substances) which ultimately influences the degree of release permitted to the aquatic environment.
Biological assessment has, historically, been more complicated to evaluate despite being the main protective goal. Many schemes rely on a points-based score derived from species diversity and abundance in collected spot samples. One difficulty with this approach is the inherent variability between river systems of endemic populations making a single meaningful national biological assessment system difficult to establish, as rivers with differing hydrology, pH, conductivity and underlying geology provide naturally differing habitats with associated variations in faunal diversity. Nevertheless biological assessments have necessarily been developed, such as the BMWP (Biological Monitoring Working Party) scheme used in England & Wales and further developed by SEPA's ASPT Environmental Quality Index (Scotland). The United States EPA is developing a more sophisticated modeling approach to its ecological assessment, utilising GIS mapping together with geomorphological data, plankton survey data and micro- and macro-faunal information to classify specific sections of river within specific states. Whilst this more complex approach may provide good quality local ecological assessment, cross-comparability can prove difficult.
In addition to ensuring environmental protection, regulators have other objectives for their river quality assessment schemes. Microbiological criteria exist in many countries with an eye to human health protection. Public relations requirements also mean that many regulators now assess aesthetic quality. This has proved important as publically-funded regulators have in the past been criticised for making observably “dirty” rivers (e.g. garbage on banks, more an aesthetic issue than a genuine threat to riverine ecosystems) of “good” quality, leading to public distrust in assessment processes.
Clearly many underlying scientific, objective criteria underpin river quality assessments. Regulators generally undertake completion of their assessments with an output easily digestible by non-professionals, such as an overall grade. This is normally phrased from “excellent” to “very poor” river water quality, though nomenclature differs nationally. There is an interesting difference in the way some regulators come to their final overall assessment. Some schemes allocate points to each of the criteria (chemical, biological, microbiological, aesthetic, etc.) and grade the river section accordingly to an overall aggregate score. Other schemes (e.g. SEPA's) grade each assessment criterion separately and assign an overall grade based on the single worst grade. The former approach provides a sound overall assessment, but may under-emphasise particular localised issues with aspects of poor water quality, whilst the latter, arguably harsher, approach can lead to severe down-grading of generally good water, but it focuses attention on specific problem areas.
The control of emissions to the environment from major polluting point sources has played an important role in improving river water quality over past decades. Identification of key polluting sources and the location of discharge emission is now well established across much of Europe, the USA and Australia. Furthermore, the recognition of hazardous substances is well developed, with regular reviews of dangerous substance lists allowing the incorporation of newly manufactured substances or contaminants where research has newly identified adverse environmental impacts.
Figure 1 shows trends in a river water quality indicator in England over a period of about two decades together with data indicating the number of serious pollution incidents. Here, a national regulator, the NRA (National Rivers Authority) was set up in 1989 following a period where water quality monitoring was largely undertaken by the operators of the water industry who were some of the more significant polluters at the time. The pattern of water quality improvement is, however, not continuous. Underlying factors must also be considered when evaluating the effectiveness of a regulatory approach to environmental protection. As the NRA began to widen its monitoring network more stretches of river water, including many smaller rivers and tributaries with severe existing water quality problems, were incorporated into the assessment, leading to a steady rise in reported pollution incidents in England & Wales from 1989-1992 (25499, 28143, 29372 and 31673 for the respective years, though the severity of each incident is not indicated here). This was a matter of the identification of existing problems rather than a real deterioration in environmental protection. Also, importantly, a change in classification approach to the general quality assessment scheme occurred in the early 1990's, making direct comparisons under prior schemes difficult and sometimes misleading and the organisation itself changed (to the current Environment Agency, EA) in 1996.
The deterioration in river quality during the mid 1990s is notable (Figure 1). The reason was a period of unusually dry weather, resulting in poorer dilution of discharges to rivers and hydrological conditions that reduced natural re-aeration rates. However, the general pattern over the period presented shows considerable improvement in terms of both the extent of higher classified rivers and in lower annual numbers of severely polluting incidents, largely achieved through focused regulation of important point-source pollution.
The regulatory approach to point-source pollution has not remained static. Recent developments have moved away slightly from fixed discharge concentrations (e.g. fixed national environmental quality standards) to an approach that evaluates an acceptable discharge quality on a site-specific basis (Figure 2). The ongoing re-licensing of major industry discharges under European Integrated Pollution Prevention and Control (IPPC) is a good example of this. Here regulators are re-evaluating existing discharge licenses in the context of the receiving environment at specific individual sites often utilising impact modeling. Formerly non-licensed substances have been added to the controlled releases in many cases to improve environmental protection, whilst other operators have benefited from a relaxation of their consents where modelling has shown their impacts will be minimal. New licenses now sometimes additionally incorporate nutrient (N, P) limits to ameliorate eutrophication or recently recognised hazardous substances including EDC's.
In principle, a locally informed approach to regulation is sensible, but normally requires the collection of monitoring data (both for the ambient environment and discharge quality) and adequate impact modeling and assessment, both of which are viewed as expensive exercises. This more specific approach is, however, achievable with modern technologies and techniques. It is possible to create first-stage impact models using simple spreadsheet-style packages. Discharge fluxes and equations that simulate a range of dispersive environments can generate data indicating whether adverse impact environmental concentrations are likely to result. Where this mathematical screening indicates potential problems, there is a wide choice of modelling software to assist the impact assessor in a refined evaluation.
There has also been significant development of the chemical analytical capabilities of regulators over recent years using highly automated sample analysis processes. Laboratories can generate millions of sample data weekly for a very wide range of substances using instruments with auto-samplers capable of running 24 hours a day largely unmanned. Data can be captured directly from the computer-controlled instruments directly into secure laboratory information systems (LIMS), with full analytical quality-control checks part of the routine and bar-coded sample tracking. Trigger alert values for samples can be set so that only those samples with unsatisfactory concentrations of contaminants need be looked at specifically by regulators. Technological developments, used for example by the UK EA, allow a small number of national laboratories to manage samples from extensive national monitoring networks for ambient and discharge monitoring.
Many developed countries now have well-established controls over point-source discharges and river water quality has improved as a consequence. However, rivers still suffer deteriorated ecological health despite direct regulation. Much of this problem appears to derive from the cumulative effect of small inputs across many discharges that tend to be under-estimated. Whilst some of these smaller inputs derive from already regulated discharges, some contaminants, notably nutrients, come largely from non-point sources (Figure 3). This is a more difficult problem to address.
Over the past 5-10 years in particular, the issue of how to tackle non-point source inputs has been a strong focus for regulators. Many have made efforts to educate polluters (industries, agriculture, urban planners) on how to reduce fugitive losses through structural and procedural best management practices (BMP's). In the USA (e.g. Florida) and elsewhere structural BMP's have been at the forefront in methodologies to reduce the flow of nutrients, pesticides and particulates to rivers through the use of retention and/or detention ponds, many of which flow to designed permanent wetlands. Essentially contaminated run-off which formerly was rapidly directed in rivers is slowed allowing settlement, filtration through soil surfaces and time for a degree of self-purification and microbial clean-up to take place. A similar approach in Malmo (Sweden) utilised old natural drainage maps to inform planning decisions in how to site BMP wetlands which also helped with water management from a flood protection viewpoint. Roadside swales are now fairly commonplace across the USA and Europe, working to retain oily residues, whilst porous road and pavement-surfaces provide another engineering solution to detain rapid run-off.
Procedural BMPs, under a variety of initiatives and names, have been successful in reducing fugitive losses from both industry and agriculture. For example, control of fugitive loss from large industrial sites is specifically evaluated under European IPPC legislation and where fugitive losses are deemed unacceptable, improvement conditions and associated implementation time-scales can be imposed. Land management best practices and environmentally sensitive farming procedures have been taken-up to a good degree across Europe and USA with a particular effort to reduce releases of nutrients, oxygen-demanding slurries and pesticides to rivers. These include planting cover-crops, well managed fertiliser application rates and techniques made under appropriate weather conditions, and the sensitive siting of potentially harmful substances within farm boundaries.
BMPs have proved successful in USA, Sweden and elsewhere in terms of general water management and reductions in river contamination whilst also being financially sound in many locations. Some success in the reduction of nutrient loads in rivers has been reported, for example in the UK where N and P concentrations have fallen in targeted basins. Studies, however, continue to show a very widespread problem with freshwater eutrophication world-wide, and whilst often voluntary BMP practices will ultimately help reduce nutrient releases, policy-makers and regulators are developing management frameworks that they hope will tackle this difficult polluting impact as part of a new approach.
Risk-based assessment, in contrast to the setting of fixed environmental quality standards, is becoming the approach of choice in many countries. In Europe, the incoming Water Framework Directive (WFD) sees regulators looking at a whole river-basin management approach to pollution control and abstraction management. This emulates an approach already used across many US states. A catchment-based approach offers several advantages over simple discharge consents over discrete polluting point-sources. For example, the cumulative effects of minor inputs of nutrients, metals and organic compounds over a wide area can result in river quality deterioration despite each individual source being either too small to cause significant local impact or being of a fugitive nature that is difficult to monitor accurately. By examining the health of the whole basin, specific measures can be put in place to control problem areas such as over-abstraction or nutrient releases. The WFD continues the evolution of quality assessment methodologies, notably by attempting to generate a biological quality rating system using the “worst case” model for finalising overall quality from a number of criteria that also recognises the need for inter-calibration across Europe.
To control nutrient fluxes, extra requirements may be made of already regulated discharges to improve nitrogen and/or phosphorus treatment. In combination with a stronger focus on BMP-style management approaches either by education or by more direct regulation, it is envisaged that nutrient losses to sensitive water habitats can be reduced in time and the difficult problem of eutrophication can begin to be addressed successfully. Stronger regulation of releases may not necessarily result in immediate environmental improvements due to other underlying factors. Phosphorus may take a long time to be naturally removed from a river system, since it binds strongly to suspended particles and sediments to be slowly re-released over time. Nitrogen, though much more soluble, also undergoes complex environmental cycling processes and may be more difficult to remove than simply shutting off the additional anthropogenic releases would imply.
River water quality has improved in countries where regulators have focused on the control of major polluting sources and river systems seem to have the capacity to recover relatively quickly when adverse impacts are curtailed. By targeting the most serious polluting substances from the major points of input, good success has been achieved in terms of environmental protection and environmental improvement. Regulators typically meet additional objectives in their river quality classification exercises, including fair treatment of polluters and achieving a reasonable degree of public confidence.
As point-source pollution has been largely well controlled throughout much of the industrialised world, regulators have shifted the emphasis to control of diffuse and fugitive sources through the promotion of best practices, both structural and procedural, with some evidence of success.
Pollution control has evolved in an effort to achieve environmental improvement. A risk-based approach to discharge control is prevalent, utilising enhanced monitoring and predictive impact analyses facilitated by technological advances. More frequently, sites are individually assessed for their impacts and their consents are adjusted accordingly. The impacts of fugitive and diffuse-source releases is being approached more holistically using a catchment-based assessment to identify ecologically damaging influences and making regulatory decisions in the light of more extensive information.
Contact:
Dr Mike Coffey is a specialist technical author at Clarity Authoring. Contact via www.clarityauthoring.com.