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Water

Public Water Supplies, Yield and Demand: 1981/1982 to 2003/2004

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. The fall in yield between 2002/2003 and 2003/2004 is principally due to including only those sources that are currently operational. For 2003/2004, daily demand includes an estimated 48% lost through leakage. ¹

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 80% of daily demand in 2003/2004, compared with 70% in 1981/1982. In contrast, metered demand decreased from 28% to 20% of daily demand.

SOURCE: SCOTTISH WATER 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.

Between 1991 and 2003 the percentage failure for total coliforms fell from 7% to 0.9% and the percentage failure for faecal coliforms fell from 3% to 0.1%.

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 0.1% of samples failing this test in 2003.

SOURCE: SCOTTISH EXECUTIVE DRINKING WATER QUALITY DIVISION ²

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 10km ² or more. Rivers are classified as excellent, good, fair, poor or seriously polluted according to measures of chemical, biological, nutrient and aesthetic quality. Between 2000 and 2004 the length of 'unclassified' river fell by 70% to 3,807 km.

Between 1999 and 2004, the length of poor and seriously polluted rivers in Scotland fell by 400km. SEPA has set a target of a reduction of 351km in poor and seriously polluted rivers for the period 1999-2006. ⁴ Poor biological and nutrient quality are the most frequent reasons for classifying rivers as poor or seriously polluted.

SOURCE: SCOTTISH ENVIRONMENT PROTECTION AGENCY

Percentage of sites within band⁶

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, and this can have harmful effects upon fish and other aquatic, life a process 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. The main source of nitrates in freshwater is run-off from agricultural land.

Concentrations of nitrate below 0.3 mg N/l are considered to be natural or background levels; ⁷ over one-third of the sites met this classification in 2004. Between 1993 and 2004 the percentage of sites with average nitrate concentrations =2.5 mg N/l rose to a peak of 25.5% in 1997, before falling to 17.6% in 2004.

Regulations have been made designating 14% of the area of Scotland ⁸ as Nitrate Vulnerable Zones ( NVZs). ⁹ In NVZs mandatory rules on farming practices aim to reduce nitrate water pollution from agricultural sources.

SOURCE: SCOTTISH ENVIRONMENT PROTECTION AGENCY

Percentage of sites within band^6,11

Excess orthophosphate in freshwaters can lead to eutrophication. The main sources of orthophosphate are outputs from sewage treatment works and diffuse pollution from agriculture.

Between 1993 and 2001 there was some fluctuation in the distribution of mean orthophosphate concentrations, with reduced precipitation in 1996 and 1997 increasing the percentage of sites with mean concentrations =250 µg P/l. Over this period the percentage of sites with mean concentrations <25 µg P/l and =125 µg P/l averaged 45% and 16% respectively. By 2004, the percentage of sites with mean concentrations <25 µg P/l had increased to 58% and the percentage of sites =125 µg P/l had fallen to 7.5%. This reduction in orthophosphate concentrations is in part due to the installation of orthophosphate removal facilities in 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 86% in 2003. Compliance rates for trade effluent and public sewage discharges have both risen by 10% since 1996-1997. Private sewage discharges show a 23% increase in compliance rates since 1996/1997 but have fallen from a peak of 81% in 2001/2002. SEPA has set a target of 95% compliance for licences issued under the Control of Pollution Act by 2003/2004. ¹⁴

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 2004, 93% of identified coastal bathing waters achieved the mandatory standard, and 55% also complied with the guideline standard.

It is important to note that the weather is thought to affect compliance, with wet weather often contributing to poorer results and, conversely, drier, hotter weather associated with better results. The fall in compliance rates between 2003 and 2004 may have been a result of the extremely wet weather of 2004.

SOURCE: SCOTTISH ENVIRONMENT PROTECTION AGENCY

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