Managing phosphorus water pollution in an uncertain future

An Oxford-led study suggests that multiple strategies may be needed to manage phosphorus in rivers. Sources of phosphorus pollution vary depending on future changes in rainfall and runoff under different scenarios of climate, land use and water resource management.

Phosphorus causes eutrophication or over-fertilisation of rivers, a serious problem that leads to excessive growth of algae, having a harmful effect on plant and animal life. Managing phosphorus levels in rivers is therefore a major global, national and European concern. Phosphorus can come from diffuse sources such as agricultural fertilisers or point sources such as sewage treatment works.

The study, led by Dr. Jill Crossman and Prof. Paul Whitehead, assesses how the water quality and hydrology of the Thames River system respond to future changes in climate, agricultural land use and water resource allocations. It then evaluates the effectiveness of phosphorus management strategies under these scenarios of future change.

The authors of the study found that the relative contribution of phosphorus from diffuse and point sources vary according to future rainfall and runoff. During high flow periods, agricultural diffuse sources are the main problem, and during low flow periods point sources dominate.

The study suggests that the best approach to phosphorus management may be to adopt multiple strategies for use at different times and locations in order to target the dominant source.

Read the full journal article in Science of the Total Environment

Proportional water allocation policies help federal countries cope with drought extremes

Dr. Dustin Garrick (School of Geography and the Environment, Oxford Martin School) delivered a presentation on drought management in federal rivers at a conference on Water in the Anthropocene, held in Bonn on 21-24 May.

Garrick and colleagues compared water allocation policies used to divide water and spread drought risk between state jurisdictions in federal countries, analysing the Colorado, Ebro and Murray-Darling Rivers. He highlighted the importance of proportional allocation rules to cope with climatic variability. Proportional allocation rules distribute water based on a share of available water – not a fixed volume or priority.

Allocation reforms in the three rivers indicate that proportional allocation rules are prevalent among upstream states, while downstream states seek fixed volumes to increase water security. The comparative study suggests that proportional rules distribute risks and benefits in a way that is perceived as fair and limits conflict when compared with fixed allocation systems.

The conference ‘Water in the Anthropocene: Challenges for Science and Governance. Indicators, Thresholds and Uncertainties of the Global Water System’ was organised by the Global Water System Project.

A Declaration signed by the participants of the conference warns that within one or two generations, the majority of the nine billion people on Earth will be living under conditions of severe pressure on fresh water, due to climate change, pollution and overuse.  However, these experts assure that this outcome is entirely avoidable. The Declaration calls for a partnership of scientists, public stakeholders, decision-makers and the private sector to take action to protect and conserve water systems worldwide.

Read the Bonn Declaration on Global Water Security

Visit the conference website

Special issue of Ecological Economics examines water allocation policy and transaction costs

Dr. Dustin Garrick (School of Geography and the Environment, Oxford Martin School), co-edited a special issue of Ecological Economics on transaction costs and environmental policy, featuring papers on water, carbon, biodiversity and land use issues. Three papers examine water allocation reforms and deliver insights about institutional responses to water allocation tradeoffs.


Transaction costs are comparably high for water allocation challenges because property rights are complex and contested. By clarifying conceptual issues and taking stock of empirical evidence and methodological innovations, this collection of papers stimulates more attention to transaction costs in environmental policy design and evaluation and provides recommendations to improve policy choices.

In a comparative study of water markets in the US and Australia, Garrick and colleagues highlight the need for flexibility to adjust water rights and diversion limits in response to policy learning. The study illustrates how the measurement and evaluation of transaction costs can encourage policy choices that improve water market performance and build capacity to adapt to climatic variability and competition.

Visit the special issue Transaction Costs and Environmental Policy online