Irish Water Technical Report on Requirement for Specific Usage Prohibitions in the Greater Dublin Water Supply Area

Transcription

1 29 th June 2018 Irish Water Technical Report on Requirement for Specific Usage Prohibitions in the Greater Dublin Water Supply Area Under Section 56(16) of the Water Services Act 2007 (S.I ) and Water Services Act 2007 (Commencement) Order 2007 (S.I. No. 528 of 2008), art. 2 IW/FF/LDB/ Irish Water [Type Document Title]

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3 1. Note of Technical Expertise Angela Ryan MSC BEng (Hons) C. Eng MIEI I am a Water Resource Specialist, working within the Asset Management Section of Irish Water. I am a Civil Engineer by training and hold a BEng (Hons) in Civil Engineering and an MSc in Civil and Environmental Engineering. I am a Chartered Engineer and member of Engineers Ireland. I am the Project Manager for Irish Waters National Water Resources Plan (NWRP). The 25 year plan will develop a roadmap for Irish Water to ensure supply demand balance for all of our 500 Water Resource Zones nationally, and will ensure that we can deliver our statutory obligations in terms of a safe reliable water supply with sufficient provisions for growth, in line with national government policy. The project includes source yield assessments, resource modelling, treatment capacity, water resource planning, growth assessment, supply demand scenario analysis and target headroom analysis for all water resource zones nationally, including the Greater Dublin Area, in order to enable Irish Water to identify where any serious deficiencies of water available for distribution exist or are likely to exist. The NWRP will also include proposals for drought and critical period planning. 2. Technical Justification for Water Restrictions Irish Water must plan for water resources on a national basis to ensure that we can source, treat and distribute sufficient water to satisfy the needs of our domestic and non-domestic users. In order to achieve this, we have split the country into spatial zones, known as Water Resource Zones (WRZs), where we continuously assess available supplies of water, against demand for water. This facilitates our identification of or areas whether any serious deficiencies of water available for distribution exists or is likely to exist. In order to protect water resources, human health and the environment, Irish Water must take a precautionary and pre-emptive approach to the prohibition and/or restriction of water supplies in order to prevent, if possible, serious deficiencies arising if it becomes apparent that they are likely to arise. The Greater Dublin Water Supply Area (GDWSA) is a Water Resource Zone, which covers County Dublin, and significant areas within Counties Kildare, Wicklow and Meath. 1 Irish Water Specific Usage Prohibitions GDWSA

4 Figure 1- GDWSA The supply area serves a population of 1.6 million people, or 40% of the entire population served by the public water supply. The average daily demand for the GDA in 2017 was 560 million litres of water per day (34% of the national public water supply). As access to a continuous water supply is a public health issue, Irish Water, must ensure that it can maintain supplies during most weather conditions, including drought conditions. In times of drought, the amount of water we have available for supply in our water sources comes under pressure as there is insufficient rainfall to replenish the reservoirs and rivers from which we abstract. During drought periods we also experience an increase in demand for water for example, as households and business begin to use water for irrigating gardens or for recreational use such as filling swimming pools. The technical justification for the proposed restrictions and/or prohibitions involves ascertaining that we are actually experiencing a drought, and evidencing either decrease in water availability and/or increased demand for water that will result in a risk of failure of the overall water supply network. Irish Water must take a precautionary and preemptive approach to the prohibition and/or restriction of water supplies in order to prevent, if possible, serious deficiencies arising if it becomes apparent that they are likely to arise. In considering the imposition of any restrictions and/or prohibitions and the extent and duration of them, Irish Water must and has considered the potential hardship to and economic impacts on domestic and commercial water users. 2 Irish Water Specific Usage Prohibitions GDWSA

5 2.1 Evidence of Drought Met Éireann has defined drought in Ireland is fifteen consecutive days with less than 0.2mm of rainfall, and has confirmed on 27 th June 2018 that the majority of the country is officially experiencing drought conditions. 20 of the 25 national weather stations have reported rainfall of less than 0.1mm over the past 15 days, including the three weather stations in the GDWSA, Dublin Airport, Casement Aerodrome and Phoenix Park. There is no forecasted rainfall in the region for the next five days and June 2018 has been the driest month on historical record. Irish Water has developed a drought indicator using the Standardised Precipitation Index (SPI) method, advocated by the World Meteorological Organisation. The indicator has been developed for representative sites across the country comparing rainfall accumulations to the long term average. We have used as the comparison period. The SPI index can be produced for different time periods to reflect the pressures on demand and different source types. The draft National Water Resources Plan proposes the following definitions for drought stages rated to SPI. Drought Stage Trigger Normal SPI above -1. Potential Drought Drought Emergency (Severe Drought) Post-Drought Table 1 Drought Indicators SPI of -1 or below SPI of -1.5 or below SPI of -2 or below The SPI metrics for 2018 to date are as follows: Recovery in supply position and easing of environmental stress SPI accumulation period Month Monthly rainfall (mm) 1month 3 month 6 month 9 month 12 month Jan Feb Mar Apr May Jun Table 2 SPI Index 2018 The SPI values for June 2018 suggest a Severe Drought, and in terms of customer demands, indicates that there is likely to be a serious deficiencies of water available for distribution in our water resources network. Summary: Evidence of Drought has been established. 3 Irish Water [Specific Usage Prohibitions GDWSA

6 2.2 Supply Demand Balance Supply/demand balance review involves calculating the maximum amount of water available from our water resources at present and comparing this against the demand for water. The GDWSA is supplied via 7 individual sources, with a maximum sustainable production of 611 million litres per day. However 84% of the supply comes from Ballymore Eustace and Leixlip Water Treatment Plants (highlighted below), which abstract from the River Liffey. Both of these treatment plants are reliant on water levels in Poulaphouca reservoir in the Wicklow Mountains. Water Treatment Plant Est. Curr. Capacity Ballymore Eustace 308 Leixlip 205 Roundwood \ Vartry 55 Ballyboden 15.5 Bog of the Ring 2.5 Srowland 22.5 Wellfields 3 Total Table 3 - Current Sustainable Supply GDWSA Poulaphouca Reservoir is an inline river reservoir formed by the construction of a concrete dam on the river Liffey in the upper catchment. The reservoir is owned and operated by the ESB, and water levels at the site must consider, dam safety, downstream flooding, water supply and electricity generation. Based on these conflicting requirements, there is a maximum amount of water that can be stored in the reservoir. The rainfall in the upper catchment is then retained by the dam for use across the course of the year, normally referred to as 226 days storage. 4 Irish Water Specific Usage Prohibitions GDWSA

7 Figure 2 Target Storage Curve Poulaphouca Maximum storage occurs across the winter period when the volume of rainfall is greatest, while water levels drop during the summer period when there is less rain. Based on historical flow sequences in the catchment we can develop a reservoir storage curve, which shows the optimal storage profile to ensure water for the output volume required. In the case of Poulaphouca, the profile must allow for 318 Ml/d abstraction at Ballymore Eustace WTP, 130 Ml/d in compensation flow to maintain ecological flows on the river Liffey and 215 Ml/d for abstraction at Leixlip WTP. Figure 2 shows the storage curve developed for Poulaphouca Reservoir. The blue line shows the actual reservoir levels, and the red area shows the failure zone. If the water level enters this zone the probability of failure increases beyond the design risk return period of the site. In terms of impact, this could involve outages for up to 500,000 water users, domestic and non-domestic for a period of over two weeks. As can be seen from figure 2, the water level in the reservoir is tracking 1 day above the failure curve. In figure 3 we have plotted historical flow sequences on this chart to assess failure later this year. In the chart, if we experienced the flows that occurred in the corresponding period for 1969 and 1995 from this day in the current year, we are at risk of supply failure at Poulaphouca, between now and December Irish Water [Specific Usage Prohibitions GDWSA

8 Daily Volume (Millions of litres per day) Figure 3 Forward outlook Poulaphouca The graph demonstrates the current vulnerability of Poulaphouca reservoir, on which 84% of our supply in the region depends. Summary: Evidence of the current vulnerability of our primary water supply been established. The average demand for water in the GDWSA for 2018 is 579 Ml/d. A maximum demand of 636 Ml/d was recorded in March 2018, due to Storm Emma. That peak in demand resulted in extensive water outages across the GDWSA region, affecting 367,000 water users Water Available for Use (Supply) & Average Daily Demand Q1 June Avge. June Max. Period of Average Daily Demand Figure 4 GDWSA Demand Profile 6 Irish Water Specific Usage Prohibitions GDWSA

9 Due to weather conditions the demand for water for the month of June has risen to an average of 586 Ml/d, with a spike in demand to 616 Ml/d on the 26 th of June. As this quantity of water is above the sustainable water supply volume, large scale outages are inevitable if demand is not reduced through voluntary reductions or restrictions in water usage. Irish Water must consider the minimum interference with water usage when considering whether it is necessary to restrict and/or prohibit water usage by domestic and/or commercial customers. Before considering the imposition of any restrictions and/or prohibitions it seeks to achieve demand reduction voluntarily from water users. If this reduction proves impossible on a voluntary basis, it must then consider the imposition of restrictions and/or prohibitions. For comparison purposes, the average demand in June 2017 was 553 Ml/d. Also, demand has never exceeded 600Ml/d in the region during the summer period. This level of demand could potentially deplete raw water levels to the extent that water supplies could be at risk of failure into autumn and Winter of this year. Summary: Evidence of the current unprecedented levels of demand has been established as has the need to reduce demand 3. Actions by Irish Water to Address Supply Demand Balance Irish Water have deployed additional find and fix leakage teams within the region, with additional crews deployed since Monday the 25 th of June. Enhanced pressure management has been in place since the beginning of June, with many areas already below optimal customer service levels. Irish Water is working to maximise the volume of water available for supply, with all Water Treatment Plants in the region at maximum sustainable production levels. To date Irish Water has conducted an extensive media campaign nationally, to encourage consumers to conserve water. The campaign has involved national and local radio, national television, social media and newspaper campaigns. The campaign has been escalated since the 25 th of June, however, this has coincided with an increase in demand of over 15 Ml/d. Summary: Irish Water has exhausted all measures to increase supply and reduce demand, voluntarily and without impacting customers 7 Irish Water [Specific Usage Prohibitions GDWSA

10 4. Additional Actions Required To date, Irish Water has attempted to reduce water demand through voluntary measures, however, this has been largely unsuccessful. If the current level of demand is not reduced it is inevitable that there will be serious deficiencies of water available for distribution, widespread supply failure and large outages across the GDWSA region. In an effort to prevent or contain the extent of outages, Irish Water proposes to exercise its powers under the Water Supply Act 2007, as amended, and to introduce measures to suppress demand through prohibiting certain non essential activities for a specified period under section 56 (16), as follows: Use of water drawn through a hosepipe or similar apparatus for the purpose of i. watering a garden; ii. iii. iv. cleaning a private motor-vehicle using a domestic hosepipe cleaning a private leisure boat filling or maintaining a domestic swimming or paddling pool (except when using hand held containers filled directly from a tap) v. filling or maintaining a domestic pond (excluding fish ponds) vi. filling or maintaining an ornamental fountain (with the exception of such use for commercial purposes) filling or replenishing an artificial pond, lake or similar application. These measures, to a large extent, involve a prohibition on non-essential customer use, and if delivered across the network, have the potential to reduce demand between 5 and 10% (based on the experience of UK water utilities). Given this is the first time these restrictions will be used, and the lack of awareness of the potential for drought amongst customers, we are expecting to achieve a 5% reduction in conjunction with an intensive communication campaign. These measures address both domestic and non-domestic users equally in relation to watering gardens and are a more equitable and controlled way of suppressing demand as an alternative to wide scale outages, that tend to impact disproportionately certain areas of the network, or vulnerable users who have difficulty sourcing water. In order to enforce these powers, as per section 56(17) of the Water Services Act 2007, Irish Water must give public notice of its intention to make an order, and specify the period for which the order will remain in force, by publishing notifications in newspapers and/or broadcasting on radio or television. Section 56(16) does not specify any notice period. Having regard to this, a reasonable notice period will be given. The notice period must also give consideration to the 8 Irish Water Specific Usage Prohibitions GDWSA

11 extent of the drought problem, the restriction of non essential activities, and the fact that unless this action is taken and demand reduced, it is inevitable that there will be serious deficiencies of water available for distribution, widespread supply failure and large outages across the GDWSA region. 5. Conclusion and Recommendation The water supply in the Greater Dublin Water Supply Area is at risk of serious deficiencies of water available for distribution and of imminent failure due to the current drought conditions that are placing existing water supplies at risk whilst causing unprecedented increases in demand for water. Met Éireann forecasts, predict no rainfall over the next five days, and existing water sources are coming under pressure with reducing water levels. Irish Water has carried out extensive measures to increase supply and to reduce demand through managing pressures in the network. Also, a large media campaign on water conservation is underway, in an effort to reduce demand voluntarily. Thus far, these activities have failed to reduce demand, which is now at unprecedented levels for this time of year. Unless immediate action is taken to reduce demand, large scale water outages will occur, across the network. In order to address this risk, Irish Water proposes to escalate efforts to reduce unnecessary usage by introducing a prohibition for a specified period on certain high water consuming non-essential activities, using its powers under section 56(16) of the Water Services Act 2007, as amended. It is proposed to restrict these activities until the 31 st of July to allow raw water sources to recover, and to mitigate against failures in the water supply later on. If it is possible to lift the notice before the specified period expires, having regard to prevailing weather conditions, availability of water resources and reduction in demand, this will be done. Equally, it may be necessary to extend the specified period for a further period and to other water users, should the prevailing conditions exist. Recommendations: Seek board approval to use powers under section 56(16) of the Water Services Act 2007 as amended to introduce a prohibition until 31st of July on non-essential high water use activities, as specified in section 4 above To develop and advertise all necessary notifications under section 56(17) To stipulate that these restrictions be maintained until the 31 st of July 2018 and that it is a criminal offence under section 56(18) not to comply with an order served pursuant to section 56(16) 9 Irish Water [Specific Usage Prohibitions GDWSA

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