Modelling and Management of Sustainable Basin-scale Water Resource Systems (Proceedings of a Boulder Symposium, July 1995). IAHS Publ. no. 231, 1995. 3 Resolving conflicts between sustainable energy and water resources in the regulation of the River Tyne, England DAVID ARCHER & GODFREY WILLIAMS National Rivers Authority, Northumbria and Yorkshire Region, Eldon House, Regent Centre, Gosforth, Newcastle upon Tyne NE3 3UD, UK Abstract Kidder Water on the River North Tyne in northeast England, the largest manmade lake in Britain, was opened in 1982 and the hydro- power plant completed in 1984. The initial operating policy, designed to optimize hydropower revenue, consisted for much of the year of a series of daily pulsed releases, reflecting the electricity supply tariff structure. The advent of a new renewable energy policy and the availability of a uniform electricity supply tariff enabled the operating policy to be revised to create an ecologically more acceptable flow regime. Methods of characterizing and comparing pre- and post-regulation flow regimes are described with particular reference to frequency and rates of change in discharge. It is concluded that a uniform tariff rate enables a pre­ cautionary approach to be taken with respect to the effect of release regime on river ecology and fisheries, without financial penalty. INTRODUCTION Kielder Water on the River North Tyne (Fig. 1) is the largest manmade lake in Britain with a surface area of 10.86 km2 and a capacity of 199.2 Mm3. It was planned in the late 1960s and early 1970s following a period of unprecedented growth in demand for domestic and industrial water supply in northeast England. It was designed as a regu­ lating reservoir to augment water resources, not only within the Tyne basin but also, by means of inter-basin transfers, using a 37.2 km pipeline, in the nearby rivers Wear and Tees (Johnson, 1988). By the time the reservoir was opened in 1982, growth in industrial demand had ceased and the projected requirement for Kielder Water to support regional water supply was not realized. Although used to regulate the River Tyne in support of water supply abstractions during the dry years of 1984, 1989 to 1992 and 1994 (Marriott & Archer, 1993), the release pattern has been dominated by the generation of hydropower. The Kielder hydropower station was built between 1982 and 1984 and power is generated by two turbines, a smaller Francis-type turbine using the compensation water release of 1.32 m3 s"1 and a larger Kaplan-type turbine with a maximum rated throughflow of 14.1 m3 s"1. At full load these generate about 0.5 MW and 5.5 MW of power, respectively, and the average annual output is approximately 20 GWh, which is fed into the national electricity grid. Hydropower is a renewable and clean source of electrical energy with no production 4 David Archer & Godfrey Williams Fig. 1 Kielder Water on the River North Tyne and the Kielder Scheme in northeast England. of pollutant emissions. Displacement by Kielder turbines of electricity generated by fossil fuel power stations would save the emission of around 8000 t of carbon dioxide, 100 t of sulphur dioxide and 30 t of nitrogen oxides per year. Nevertheless, hydropower releases to the river may have significant impact on the water environment, especially its general ecology and fisheries. The River Tyne is one of the principal salmonoid rivers of England and Wales. The National River Authority of England and Wales (NRA), who now have responsibility for designing the release policy, is concerned to ensure that negative impacts of such releases are minimized. They have reviewed and implemented policies in the light of their understanding and perception of the nature of their impact, and also to take advantage of recent changes in electricity tariff structures. The impact of the construction of Kielder Reservoir and subsequent management of discharges to the North Tyne on invertebrate and fish populations was studied by Haile Conflicts between sustainable energy and water resources in the River Tyne 5 et al. (1989). The effect of changing flows was considered to be amongst the most significant, which also included water temperature, water quality and sedimentation. Subsequent work by National Rivers Authority (unpublished) has demonstrated the strong relevance of river flows, as affected by reservoir discharges, to human use of the river as a recreational resource. In particular, success rates and perceived satisfaction with conditions amongst salmon and trout anglers have been seen to be closely related to range and pattern of flow. In this paper we outline the legal framework for hydropower generation at Kielder and the way in which changes in 1989 have enabled a more flexible operating policy to be adopted. The operating policies are described and the river regime compared with the pre-regulation regime. KIELDER HYDROPOWER - LEGAL FRAMEWORK Legal powers to construct works at Kielder for generation of electricity were conferred on Northumbrian Water Authority (NW) under the Kielder Water Order of 1974 which provided the statutory framework for the entire Kielder Scheme. Subsequent agreement between NW and the Central Electricity Generating Board (CEGB) in 1983 was made to install the generating turbines with shared capital inputs and equivalent financial benefits at a ratio of 60% CEGB : 40% NW. The parties agreed to operate the turbines for maximum economic benefit within the constraints imposed by NW's statutory obligations. These included: (a) a continuous compensation flow; (b) releases to support a minimum maintained flow of 10% of the average daily flow in the lower reaches of the Tyne and, by transfers, on the lower Wear and Tees; and (c) releases to support public water supply abstractions on each of the three rivers. In addition, a specific, allowance was made for the benefit of the North Tyne fishery, for discharges in excess of generating capacity or non-optimal discharges, to be made up to the value of lost revenue of £23 000 updated annually. Within these constraints NW devised a policy, as outlined below, to optimize gene­ rating revenue, based on expected seasonal flow variations and a complex electricity tariff structure. There were two significant British legislative measures in 1989 which encouraged the reappraisal of the river regulation policy: (a) Under the Water Act (1989) the service functions of the British water industry were privatized and a separate, independent National Rivers Authority (NRA) was established as "guardian of the water environment". The NRA has a much stronger locus in conservation and amenity than its predecessor NW, which remains the reservoir and hydropower operator. The consolidating Water Resources Act (1991) confirms both the NRA's water resources management duties of "securing the proper use of water resources" (Sec. 19) but also its environmental duties (Sec. 16): "... to exercise any power ... so as to further the conservation and enhancement of natural beauty and the conservation of flora, fauna and geological and physiographical features of special interest;... to take into account any effect which proposals would have on the beauty or amenity of any rural or urban area or any such flora, fauna, features, buildings, sites or objects". 6 David Archer & Godfrey Williams (b) The Electricity Act (1989) was the enabling legislation for the privatization of the UK electricity industry. Provision was also made within this Act for similar environ­ mental duties but more passively worded (Sec. 38, Schedule 9). A license holder shall: "have regard to the desirability of preserving natural beauty, of flora, fauna .. .etc. ; do what he reasonably can to mitigate any effect which the proposer would have on the natural beauty of the countryside or on any such flora, fauna ... etc." The Act also introduced the non-fossil fuel obligation (NFFO) which required elec­ tricity companies to derive a specific proportion of their electricity from non-fossil sources with premium prices payable for a set period of time to generators awarded NFFO contracts. The NFFO is financed by a tax on customers. Of revenue thus generated, 98% goes to nuclear power and 2% to renewable energy sources. Three NFFO renewable orders have been made under the Act, primarily to encourage new developments, but some contracts were also awarded to existing generators. The Kielder hydropower plant was accepted for a NFFO contract in late 1991 to apply for a period of 7 years. In addition to receiving a subsidized tariff rate, the tariff is applied at a uniform rate, daily and seasonally. This has permitted a generating and release policy to be devised more in sympathy with the ecology of the river, without incurring significant financial penalties. HYDROPOWER OPERATING POLICIES AND TARIFFS Policy 1 1984-1993 Following the installation of hydropower in 1984, a policy of releases to the River North Tyne was derived to maximize the revenue earned from the sale of electricity to the National Grid. The development of the control policy was a two-stage process. Firstly, a stochastic dynamic programming algorithm was developed and used to determine the weekly volumes to be released for given reservoir level and month of the year, allowing for uncertainty in future reservoir inflows (Johnson & Sanderson, 1987). The policy ensured that the reservoir stayed within a band where there was little risk of lost revenue either through spillage or through declining reservoir level and head. Secondly, a building block allocation procedure called "Golden Search" was used to determine how the weekly volume could be allocated within each day of the week to ensure maximum revenue for a given volume. The derived release pattern was closely dependent on the structure of the electricity supply tariff which varied daily, weekly and seasonally (Fig. 2). Winter revenue was greater than summer, daytime greater than night-time, and particular advantage was gained through a "peak surcharge rate" by generating in the 1.5 h of peak system demand each day.