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Key Scottish Environment Statistics 2003

water

Public Water Supplies, Yield and Demand: 1981-1982 to 2001-2002

Average volume of water (Megalitres/day)

For sustainable management of water resources, it is essential to meet consumers' demand and standards, whilst maintaining aquatic ecosystem health. Abstraction of water has impacts on geology, habitats, wildlife, biodiversity, and recreational use of water resources. To prevent low flow levels downstream, minimum compensation flows need to be discharged at all times. Compensation flows are specified in the Water Orders made under the Water (Scotland) Act 1980.

Demand for water in Scotland has increased by 6% since 1981-1982, although yield from developed resources (representing the potential water available) is still greater than demand. For 2001-2002, daily demand includes an estimated 45% lost through leakage.

Water demand comes from unmetered and metered potable water, and small amounts of non-potable water. Unmetered demand (domestic use, small industries, public use, etc.) accounted for 78% of daily demand in 2001-2002, compared with 70% in 1981-1982. In contrast, metered demand decreased from 28% to 22% of daily demand. The decrease in metered demand may represent industry using less water to reduce water supply and waste water charges.

SOURCE: SCOTTISH EXECUTIVE WATER SERVICES UNIT ¹

The coliform group of organisms is present in large numbers in the gut of all warm-blooded animals and therefore widely distributed in the environment. Their presence in tap water indicates a breach in the integrity of the water supply system.

The 1990 Water Supply (Water Quality) (Scotland) Regulations set strict standards for compliance and the success rate varies across Scotland. The major centres of population are served by water treatment works, which are generally well equipped to achieve the standards set. Infrequent minor and low level failures with little implication occur at these works. Rural areas not served by treatment works can have water of variable quality.

The Water Quality 1000 index, ² based on 10 key parameters including faecal and total coliforms, has fluctuated since 1992, but has been increasing since 1998, reaching 976 in 2000.

The standard set by the Water Supply Regulations, for 95% of samples to be free of all coliforms, has been met every year since 1992. However, the strict standard of zero faecal coliforms in all samples has not yet been achieved, with 0.2% of samples failing this test in 2000.

SOURCE: SCOTTISH EXECUTIVE WATER SERVICES UNIT ³

Length (kilometres)

Low standards of river water quality may threaten the aquatic environment, drinking water quality and recreational water use. Sewage, industry, urban development and agriculture are some of the factors that may affect river water quality.

The Scottish Environment Protection Agency (SEPA) has established a Digitised River Network (DRN) to classify about 25,000km of the approximately 100,000km of rivers and burns in Scotland. The DRN comprises those watercourses draining a catchment of 10km2 or more, and classifies rivers as excellent, good, fair, poor or seriously polluted according to measures of chemical, biological, nutrient and aesthetic quality.

Between 1999 and 2002, the length of poor and seriously polluted rivers in Scotland has fallen by 210km. SEPA has set a target of a reduction of 351km in poor and seriously polluted rivers for the period 1999-2006. ⁵ Poor biological and nutrient quality are the most frequent reasons for classifying rivers as poor or seriously polluted.

SOURCE: SCOTTISH ENVIRONMENT PROTECTION AGENCY

Annual average concentrations (mg/l)⁶

The enrichment of waters by nutrients, such as nitrates and phosphates, can damage the aquatic environment through the accelerated growth of algae and other plant life. The rapid growth and subsequent decay of plant organisms depletes oxygen levels, which may have harmful effects upon fish and other aquatic life. This process is known as eutrophication.

High nitrate levels have a greater impact on marine and coastal waters than freshwater, although nitrates in freshwater will eventually reach the sea. Nitrates in drinking water supplies also pose a risk to human health. The main source of nitrates in freshwater is run-off from agricultural land.

The highest average nitrate concentrations in rivers are found in the SEPA South East area. Concentrations in the South East and South West have fluctuated. In the Highlands, Islands & Grampian, there was a steady increase throughout much of the 1980s and 1990s, but levels have fallen since 1998.

Regulations have been made designating 14% of the area of Scotland ⁷ as Nitrate Vulnerable Zones (NVZs). ⁸ In NVZs, mandatory rules on farming practices aim to reduce nitrate water pollution from agricultural sources.

SOURCE: SCOTTISH ENVIRONMENT PROTECTION AGENCY

Annual average concentrations (mg/l of phosphorus equivalent)⁶

Excess phosphorus in freshwaters can lead to eutrophication. The main sources of phosphorus are outputs from sewage treatment works and diffuse pollution from agriculture. Orthophosphate levels provide a good indication of trends in total phosphorus.

Orthophosphate concentrations in the SEPA South East and South West areas show a similar trend over the period 1986-2002, with levels in the South West being slightly higher, in general. The fluctuating nature of the concentrations over the period may be due to factors such as the river flow variation between years. Since reaching a peak in 1996, orthophosphate concentrations in both areas have fallen. This decline may be partly due to the installation of phosphate-removal facilities at sewage treatment works.

Under the Urban Waste Water Treatment Directive (UWWTD) (91/271/EEC), the Ythan Estuary, Dean Water, South Calder Water, River Almond, the lower part of the River Don and their respective catchments are all designated sensitive areas. Discharges into waters that have been designated as sensitive require additional treatment to remove nutrients.

SOURCE: SCOTTISH ENVIRONMENT PROTECTION AGENCY

Samples complying with relevant standards (Percentage)

Under the Control of Pollution Act (1974) it is an offence to cause or knowingly permit discharge of poisonous, noxious or polluting substances to controlled waters in Scotland. Discharges of sewage and trade effluent into controlled waters, including all coastal and inland waters may, however, be made under a discharge consent authorised by the Scottish Environment Protection Agency (SEPA). Authorisations contain conditions on both the quality and quantity of effluent permitted. SEPA control these discharges through licensing and monitoring.

Point source sewage effluent is currently the most important source of pollution affecting tidal waters in Scotland.

The overall compliance rate increased from 73% in 1996-1997 to 85% in 2001-2002. Compliance rates for trade effluent and public sewage discharges have risen by 7% and 10% respectively since 1996-1997. Private sewage discharges show a 30% increase in compliance rates since 1996-1997. SEPA has set a target of 95% compliance for licences issued under the Control of Pollution Act by 2003-04. ¹⁰

SOURCE: SCOTTISH ENVIRONMENT PROTECTION AGENCY

High quality bathing waters are important for a wide variety of interests and support Scotland's tourism industry. Monitoring the quality of these waters provides an indication of the health risks of bathing from both direct and diffuse discharges of effluents containing faecal contaminants.

EC Bathing Water Directive (76/160/EEC) sets out two quality standards - the 'mandatory' standard, and the stricter 'guideline' standard. Member states should comply with the mandatory standard and aim to comply with the guideline standard.

In 2002, 91% of identified coastal bathing waters achieved the mandatory standard, and 41% also complied with the guideline standard. The 2002 compliance rate for the mandatory standard is the highest on record, along with 1996.

It is important to note that the weather is thought to affect compliance, with poorer results often associated with high rainfall.

SOURCE: SCOTTISH ENVIRONMENT PROTECTION AGENCY

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