8.1 Environmental Objectives
8.1.1 Objectives relating to the condition of all water bodies are set through the Water Framework Directive  , which governs objectives for rivers, lochs, transitional waters, coastal waters, and groundwater resources. The Water Framework Directive sets out the requirement for an assessment of both chemical and ecological status, alongside the requirement to consider the status of biodiversity as an indicator in determining water quality.
8.1.2 These objectives are set in the Scottish context in a range of water, coastal and marine policies. Scotland's two River Basin Management Plans  aim to improve the overall condition of water bodies. The protection of Scotland's water resources has also been translated through the establishment of legislation and regulations such as the Water Environment and Water Services (Scotland) Act 2003  and the Water Environment (Controlled Activities) (Scotland) Regulations 2011 as amended  . These complement the role of others such as the Pollution Prevention and Control (Scotland) Regulations 2012  , developed to specifically control pollution relating to industry discharges.
8.1.3 The Flood Risk Management (Scotland) Act 2009 and subsequent regulations and orders  provide for the management of flood risk and translate the EU Floods Directive  to the national context.
8.2 Environmental Context
8.2.1 Scotland's water resources provide a wide range of benefits across a number of environmental topic areas. Together with other environmental topics, including soil and air, water resources play a key role in supporting the health of our ecosystems and, in doing so, also make a significant contribution towards sustaining our health and prosperity. They also support a diverse array of habitats and nationally and internationally important species such as Atlantic salmon and freshwater pearl mussels.
8.2.2 In recent decades, significant improvements in water quality in many rivers, canals and estuaries have been observed, and there have been significant reductions in pollution. However, rivers across Scotland's central belt and east coast require additional work to achieve Scotland's overarching target of all water bodies achieving 'good or better' for overall status  .
8.2.3 Key pressures on the surface water environment originate from human activities and include urbanisation, intensive agriculture/aquaculture and climate change. Rural and urban diffuse pollution also remains a concern for water quality  . For example, runoff from hard surfaces in urban areas may be contaminated with oil, petrol and toxic metals which can then be washed into drains, polluting nearby watercourses.
8.3 Assessment Findings
What are the likely implications of increased passenger and flight numbers on water resources?
8.3.1 The following paragraphs set out the potential impacts to water resources which are considered likely to arise from increased activity in the aviation sector, based on the assumptions that the implementation of the policy will lead to increased flight and passenger numbers. These secondary impacts are considered outwith the ability of the policy option to influence.
8.3.2 Airport related development and aviation activity can affect water quality in several ways, including run-off from buildings and hard surfaces and through the use and accidental spillage of potential pollutants such as fuel and de-icing fluids. It has been considered that growth in the sector has the potential to lead to the requirement for expansion of supporting infrastructure if current capacity is exceeded, which could increase the proportion of hard surfaces and the potential for run-off. Additionally, ground activities may increase in line with growth in the sector, such as an increase in the use of fuel and chemicals for maintaining operations. Construction and development activities can also negatively impact on water quality.
8.3.3 The potential for impacts on water quality arising from airport development was considered during the assessment of the proposed Strategic Airport Enhancements in the NPF3. The assessment noted that short-term impacts on water quality from construction activities could arise, with additional potential for long-term impacts stemming from operational activities. In addition, specific water courses, such as the Firth of Forth and its tributaries and the Black and White Cart Waters, were identified as potentially requiring further consideration with regards runoff and flood risk implications  .
8.3.4 Additionally, the effects of climate change are predicted to be an increasing pressure and likely to present a significant challenge to ambitions for improving water quality  . The contribution of the aviation sector to climate change is considered further under the topic of Climatic Factors.
8.3.5 The degree to which the identified increase in passenger numbers will be realised will influence these secondary effects. This has been considered though the illustrative scenarios. For example, if a greater number of passengers over current levels were to be experienced, this would place further pressure on water resources as airports are large consumers of water  .
8.3.6 A reasonable alternative to the preferred policy option is that there is no reduction in the overall tax burden of ADT. It is considered that this represents a "like for like" approach as the tax rate amounts would remain the same as those currently set under UK APD. Under this approach there would be no reduction in the tax burden and, as such, it is considered that there would be no additional direct impact on passenger and flight numbers and therefore no potential affect water on resources.
What wider context and mitigation measures should be taken into account?
8.3.7 There are strict rules in place around the storage and handling of fuels, and advice is provided on the environmental impacts of de-icing chemicals used in aviation  . Airports are also investing in improved handling facilities and processes to reduce the risk of groundwater or surface water pollution from de-icing and fuel handling equipment  . In addition, through the Water Environment (Controlled Activities) (Scotland) Regulations 2011 as amended  , any new water discharges by airport operators would require the permission of SEPA.
8.3.8 Any future airport and supporting infrastructure development would be outwith the remit of the preferred policy option to influence. In addition, it is likely that any significant proposals for any infrastructure works will be required to undertake an EIA. Further project level assessment, including EIA screening, will therefore be required.
8.3.9 Water consumption is considered as part of an airport's sustainability performance or corporate responsibility. These reports set out information such as monitoring and conservation measures for that airport.
What is the likely significance of the predicted impacts?
8.3.10 At this stage of the SEA process it is difficult to predict with any degree of certainty the extent and significance of the identified impacts that may arise from infrastructure requirements.
8.3.11 It is assumed that the preferred policy option will lead to increased growth in the aviation sector, placing further pressure on existing airport infrastructure. This will further be influenced by the extent to which the anticipated increase in passenger numbers is realised. Any proposed works that may be required to facilitate this growth will also be influenced by a number of factors, such as other strategies that seek to create sustainable transport links.
8.3.12 Due to the nature of the identified changes, it is considered that the likely impacts will be realised at a local level, with the significance of these dependent on factors such as the scale and location of any proposed development and specific operational activities at individual airports. Long-term impacts from operational activities are considered likely, in addition to short-term impacts arising from construction activities. Further to this, there may be national level implications for water resources as a result of climate change.
Box 8.1 Water: Summary of impacts and key points