WATER SUPPLY AND THE HYDROLOGICAL CYCLE : THE CASE IN IRELAND

WATER SUPPLY =

PRIMARILY A HYDROLOGICAL PROBLEM

Paul Johnston & Laurence Gill,

Civil and Environmental Engineering,

Trinity College Dublin October 2011

Joint Committee on Environment, Transport, Culture and the Gaeltacht

THE WATER SUPPLY PROBLEM IN IRELAND :TOO MUCH WATER IN THE WRONG PLACE

(AT THE WRONG TIME)?

RAINFALL IS THE PRIMARY SOURCE OF WATER SUPPLY (MET EIREANN)

THE WATER BALANCE IN IRELAND : RAINFALL – EVAPOTRANSPIRATION(300mm to 1000mm per year)

Source : Mills, Irish Geography, 2000

LONG TERM RAINFALL RECORDS SHOW TRENDS PARTICULARLY SINCE 1975 (Met Eireann)

Source : Simmler, Met Eireann, 2010

WATER SUPPLY STRATEGY

•Ireland has plenty of water, even increasing

•‘Shortages’ are due to increasing demand in centres that do not coincide with the areas of surplus water supply

•Hydrological conditions in Ireland mean that water/rainfall moves through the system relatively quickly : residence times in surface and groundwater are short.

•Access to the needed water can be a mix of surface and groundwater : but they are interconnected and one is not necessarily an alternative to the other.

•The proposed Shannon abstraction is equivalent to approximately 28mm of net rainfall per year over the catchment, ie about 6% of the annual total

•Water management must be holistic with a view to related ecological requirements

National Groundwater Recharge map 2009

Groundwater abstractions

GROUNDWATER ABSTRACTION BY COUNTY

INTER CATCHMENT WATER TRANSFER IS FEASIBLE BUT TAKING INTO ACCOUNT THE RISKS

•Water, unlike oil, is not consumed : it is the truly renewable resource

•‘Wastewater’ is effectively returned to the hydrological cycle

•Thus, water management must be holistic, as envisaged by EU legislation, involving the whole hydrological cycle

•Spatial variability in rainfall and hydrological conditions mean that water needs to be managed nationally (or regionally) to be effective.

•Conservation and innovative methods of water harvesting and wastewater disposal have an important role but need to be managed consistently.

•Care must be taken to separate the roles of regulation and protection from those of water supply and treatment/disposal.

•Consolidate the disparate roles of several state agencies in water management

WATER MANAGEMENT IN IRELAND

MANAGEMENT ON BASIS OF REGIONS : RIVER BASIN DISTRICTS

NATIONAL GROUNDWATER MONITORING NETWORK (EPA 2008)

MONITORING IS A NATIONAL TASK : SHOULD BE UNDERTAKEN BY ONE AGENCY/ORGANIZATION