A network of consultants in: water resources, hydrology, hydraulics, hydrogeology and water quality

Climate Change - impacts and downscaling

Climate change predictions

It is now widely accepted that the Earth’s climate has warmed since the Industrial Revolution at a rate greater than that expected through natural variation. Current predictions suggest a further rise in the global mean temperature of 3 ºC by 2100. The emissions of carbon dioxide and other ‘greenhouse gases’ such as nitrous oxide and methane, which result from industry, energy production and transport, have caused the increase in temperature.

Potential impacts

A warming climate has implications for water resources and water quality; increases in the air and sea temperatures will affect global circulation patterns, and as a result, at the regional or catchment scale, this will affect:

·         the occurrence and length of droughts;

·         the occurrence and magnitude of flood events;

·         the seasonal pattern of runoff, including the proportion of flow from snow melt.

·         the irrigation of crops and land management;

·         the cycling and transport of nutrients and pollutants within the river-system;

·         the ecology, by alterations in the flow regime and water quality.

Application of General Circulation Models

At present, it is difficult to quantify the likely impacts of climate change on water quantity and quality since there is uncertainty in future climate forecasts and how river-systems will respond. Any study of the impacts of climate change must account for this uncertainty. Climate change is expected to be greatest in the tropics and low latitudes, and therefore an assessment of these regions is as important as the likely affects in the more developed countries.

Water Resource Associates Ltd has expertise in the field of estimating the likely impacts of climate change on water resources and water quality; with experience of down-scaling the outputs from the latest General Circulation Models for use in hydrological and water quality models; dealing with the uncertainty in both climate model and hydro-chemical models; and applying models to examine adaptation strategies. In particular, two of the company’s directors are leading research on the impacts of climate change on freshwater ecosystems.

In Jordan we are working with the University of Reading on a 5-year studied finance by the Welcome Trust. This study is looking at the response of populations in the past to changes in climate and using this as a guide to responses in the future. The project combines archaeology, climatology and hydrological. The hydrological component is modelling some of the Wadis in the study area to asses the impact of climate change on runoff and water availability.

Experience as a company and directors

 Pan Europe
 A pan European model-based assessment of the factors and processes controlling nitrogen export is being done. Models of flow and nutrient dynamics have been applied at sites across the current climate gradient of Europe from the artic north to the Mediterranean. The outputs from General Circulation Models are being down-scaled for input to catchment scale water quality models. The results will then be compared across the different sites to provide a pan European assessment of the affects of climate change on nitrogen in rivers.

 In addition the Principles have also worked in:

A study of climate change for Severn-Trent Water by downscaling the results of GCMs to the Severn and Trent river basins. In this study HYSIM was used to simulate flows on all the major water resources rivers of the company. Initially it was calibrated to observed flow and climatic conditions then a range of climate scenarios was tested to evaluate the likely effect on runoff.

Two Directors of WRA were co-authors of a paper examining downscaling methodology which is being adopted as a standard in the UK. This was tested on a catchment likely to suffer water stress and the impacts on flows and water quality were examined. (Integrated modelling of climate change impacts on water resources and quality in a lowland catchment: River Kennet, UK, R.J. Wilby, P.G. Whitehead, A.J. Wade, D Butterfield, R.J. Davis, G. Watts, Journal of Hydrology (2006) 330, 204-220.)

The HYSIM rainfall runoff/model  developed by a Director of WRA and marketed by them has been used in a number of  studies of climate change impact. These include:

Assessing The Impact Of Climate Change On Water Supply and Flood Hazard in Ireland Using Statistical Downscaling and Hydrological Modelling Techniques. Rosemary Charlton, Rowan Fealy, Sonja Moore, John Sweeney and Conor Murphy Climatic Change, Volume 74, Number 4, February 2006 , pp. 475-491(17)

High resolution climate change scenarios: Implications for British runoff, Pilling, C. and Jones, J. A. A.: 1999, Hydrol. Process. 13, 2877–2895.