Compared to the Drinking Water Inspectorate's first annual report (ENDS Report 198, pp 18-20), the Scottish equivalent is preliminary and incomplete. It covers only the latter half of 1990 due to the later introduction in Scotland of drinking water regulations under the Water Act 1989.
Scottish water undertakers also had even more problems in implementing the required monitoring programmes than their English and Welsh counterparts, and the data are therefore incomplete.
Some 85% of Scotland's drinking water comes from upland reservoirs and is generally peaty, soft and acidic. The major quality problems are colour, iron and manganese, lead, aluminium and the chlorination by-products trihalomethanes (THM). Very few zones have any difficulty complying with standards for nitrate, pesticides or polycyclic aromatic hydrocarbons.
In the latter half of 1990, Scotland achieved 96.9% compliance with regulations. The compliance rate in England and Wales was 99% for the whole year.
Compliance with microbiological standards was "disappointing", the report comments. Most of the breaches occurred in smaller supply zones. Nearly 60% of Scotland's 722 zones supply fewer than 1,000 people.
The proportions of zones failing colour and THM standards were also high compared to England and Wales, but the proportions failing lead and iron standards were lower.
Just over half of Scottish supply zones (367) were the subject of improvement undertakings in 1990. The most common parameters covered were aluminium, microbiological quality, lead, THM, and iron. Time-limited relaxations were also authorised for 218 zones, mostly for colour, iron, manganese or turbidity.
None of the 12 water undertakers in Scotland complied fully with the monitoring requirements prescribed by the regulations. In some cases only 50% of the required determinations were made. Highland and Shetland Islands, for example, failed to make any tests of microbiological quality at water treatment plants or service reservoirs. Enforcement action will be needed to ensure that councils enhance their sampling and analytical resources, the report concludes.