Hydrology-phosphorus interactions under changing climate and land-use: overcoming uncertainties and challenges for prediction to 2050 (Nutcat 2050)

The proposal aims to advance our understanding and predictions of interactions between hydrology and nutrient transfers in headwater catchments in the UK, under climate and land use change scenarios to 2050, using the very latest data and modeling approaches available for the UK. The study catchments will be the UK Demonstration Test Catchments (DTCs) and the aims will be achieved through: (1) using existing climate model scenarios to set baseline outcomes for change; (2) localized DTC-focused stakeholder elicitation workshops to develop scenarios for land use changes in response to the climate scenarios; (3) simulating current hydrological events and future changes in catchment hydrology in response to changing climate/land use; (4) new understanding of phosphorus (P) behaviour in extreme hydrological conditions, using experiments and newly available high resolution observations from the DTCs to inform model development; (5) improved prediction (with uncertainty) of future P behaviour scenarios arising from the new understanding of hydrology-P interactions; (6) attempting to scale up the information from headwater-catchment to full basin scale, and; (7) compare model performance with existing P models and assess uncertainties involved in this process, with further iterations of stakeholder consultation. We shall focus on the 10 km2 scale because this matches the size of the nine study catchments of the Defra DTCs (from the Eden, Wensum and Avon DTCs), which are our chosen study areas; this scale also represents the ideal size for studying processes along the mobilisation-delivery-in-stream impact 'transfer continuum'. These integrated studies will produce a prototype quantitative assessment and prediction of nutrient fluxes.

Our hypothesis is that increased seasonal variability in storm patterns (more extreme events, long drought periods), combined with interactions with land use change, will greatly alter future dissolved and particulate P fluxes across the land-water continuum and subsequent retention in-stream and downstream eutrophication risk. We shall extend our initial 'Systems Evidence Based Assessment Methodology (SEBAM)' study that focused on mobilization of P at the farm scale (recently published by the team), into a prototype modeling framework that includes source, mobilization, delivery and in-stream processing functions for predicting P fluxes from UK headwater catchments, and considers land use change, and use this framework (combined with knowledge from other projects involving the team) to scale up our information to define the potential for predicting other nutrient behaviours at the full basin scale.

We will capitalize on the new and unique high quality, high temporal resolution P monitoring data that is starting to emerge from the nine Defra DTC sub-catchments. A unique and exciting aspect of the work will be the use of expert elicitation procedures that incorporate fuzzy uncertainty-based analyses to develop tailored land use scenarios (building on the UK Land Use Foresight Initiative) for each of the unique landscape typologies for the 9 DTC focus catchments. Combining this information with the latest climate scenarios for the UK, we will include new developments in high-resolution numerical weather prediction. We shall then use these scenarios to study the impacts of climate and land use change to 2050 on hydrology, P mobilization, delivery and in-stream processing, informed from new empirical learning and experimentation. Model outputs will then be validated for other catchments in the wider UK (Conwy, Ribble, Tarland) using data from linked projects and our partners. Throughout the project, the outcomes will be tested with stakeholders. This will deliver a locally owned knowledge-based framework for understanding and managing future nutrient transfers from rural catchment systems, and some exciting new science on P transfers.

There are many groups of potential beneficiaries of the proposed research, these include:

- Policymakers (Defra in particular, Scottish and Welsh Governments, EU): who are responsible for setting policies for sustainable rural land and water use now and the future, this project will directly support policy development;
- Water Companies in the UK (private and public): who are increasingly using catchment based approaches to manage water quality, need the approaches and data from this project to manage the risks from future climate and land use change on their water resources;
- Private enterprises and businesses (e.g. environmental consultancies): require information from this project about how to link climate and hydro-biogeochemical models and the relative performance of alternative modeling approaches to deliver projects to a broad range of clients;
- Food chain suppliers and supermarkets: require better information that this project will provide on how future climate scenarios will affect sustainable land use;
- Farming advisors (including Rivers Trusts) and extension officers: will benefit directly from the approaches, data and knowledge generated from this project on how rural land management influences P transfers from land to water now and in the future; and
- Farmers and land managers: require greater knowledge on possible future changes in climate and how this will affect their operations and losses of valuable P stocks from their soils.

These stakeholders will benefit because the work aims to improve our understanding of nutrient transfers from land to water and we shall provide new methods of predicting (and thus mitigating) what may happen in future events. They will also benefit from improved the knowledge of uncertainty and this will help them make more robust judgments about future management scenarios. All of these will contribute towards a reduction of nutrient pollution that contributes towards eutrophication of rivers, lakes and estuaries and, potentially, an increase in biodiversity.