2. Technical Justification for Water Restrictions

Transcription

1 4 th July 2018 Irish Water Technical Report on Requirement for Specific Usage Prohibitions in all Areas Served via the National Public Water Supply (excluding 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 NWRP 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. Each day, Irish Water produces an average of 1,650 million litres of water, for use by a population of 4 million people and over 180,000 non domestic users. Water is abstracted from 1,200 individual water sources, treated at 790 water treatment plants and distributed through a network of approximately 60,000 kilometers of watermains. The public water supply network does not cover the entire country. Approximately 80% of the population take their supplies from our network, while the remainder use private wells or are served via group water schemes. Public water supplies also cover the Islands off the coast of Ireland, including: County Cork Cork Cork Donegal Galway Galway Galway Galway Mayo Mayo Island Cape Clear Whiddy Island Sherkin (Supplied from main land) Arranmore Island Inisboffin Inishmean Inishmore Inishere Inishturk Clare Island 1 Irish Water Specific Usage Prohibitions GDWSA

4 As access to a continuous water supply is a public health question, 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, rivers and aquifers 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. There are also competing needs for diminishing water supplies during drought conditions, including: 1. Agricultural Needs 2. Natural aquatic environment 3. Assimilative capacities for wastewater discharges 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 National Public Water Supply (excluding GDWSA)

5 Figure 1- Irish Water Public Water Supply Network including Key Settlements 3 Irish Water Specific Usage Prohibitions National Public Water Supply (excluding GDWSA)

6 2.1 Evidence of Drought Met Éireann has defined drought in Ireland as fifteen consecutive days with less than 0.2mm of rainfall. Met Éireann: Update to drought status on 2nd July out of the 25 Synoptic stations have now 11 consecutive days with daily total rainfall less than 0.2mm (that s from 21st June 1st July) with Belmullet being the exception. So there will be an Official Absolute Drought at these stations at Midnight on Thursday 5th July if there is less than 0.2 mm rain at these stations every day up until then. In order to manage our water supplies during drought periods, Irish Water has developed a draft Drought Management Plan that uses indicators to track current weather conditions in relation to drought, identifies triggers for action as we enter drought periods and develops potential actions that can be used to maintain water supply (where possible) during these conditions Drought Indicators 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. Using monthly rainfall data from the Island of Ireland Precipitation 1 Network to provide a reference period from 1850 to 2010, as part of its draft National Water Resources Plan, Irish Water has selected ten rainfall stations that are representative of the national picture and where up to date information is available in a timely manner. The ten sites have then been spatially weighted to determine the SPI values for a management area (water resource zone) using Theissen polygons method, as seen in Figure 2. All of Irish Waters Treatment plants are located within these management areas. The SPI index can be produced for different time periods to reflect the pressures on demand and different source types. For this analysis the 1 month SPI is being used, to represent the rainfall conditions over the month of June into July Homogenization and analysis of an expanded long term monthly rainfall network for the Island of Ireland ( ) S. Noone C. Murphy J. Coll T. Matthews D. Mullan R. L. Wilby S. Walsh. First published: 05 October Irish Water Specific Usage Prohibitions National Public Water Supply (excluding GDWSA)

7 Figure 2 Rain gauge sites used in SPI calculation and Theissen polygons for spatial weighting SPI is a normalised index representing the probability of occurrence of an observed rainfall amount when compared with the data for long-term reference period at a given location. Negative SPI values represent a rainfall deficit, moving towards drought, whereas positive SPI values indicate rainfall surplus. The larger the negative SPI values, the more serious the measured event is. The draft Drought Management Plan proposes the following definitions for drought stages rated to SPI. Drought Stage Trigger Normal SPI above -1. Potential Drought SPI of -1 or below Drought SPI of -1.5 or below Emergency (Severe Drought) SPI of -2 or below Post-Drought Recovery in supply position and easing of environmental stress Table 1 Drought Indicators The public water supply in Ireland currently consists of 790 individual water treatment plants. If we contour these within the polygons the results are summarised in Table 2 and Figure 3. 5 Irish Water Specific Usage Prohibitions National Public Water Supply (excluding GDWSA)

8 Drought Stage Trigger No. WTPs % Normal SPI above -1 Potential Drought Drought Emergency (Severe Drought) SPI of -1 or below SPI of -1.5 or below SPI of -2 or below 18 2% 90 11% % % Table 2 Drought Indicators National WTPs Normal SPI above -1, 18 Potential Drought SPI of -1 or below, 90 Emergency (Severe Drought) SPI of -2 or below, 452 Drought SPI of or below, 230 Figure 3 Drought Indicators WTPs As can be seen, of the 790 Water Treatment Plants that make up the public water supply, 87% of these are located in areas, with either a drought or emergency drought SPI index. A further 11% are located in areas classified as Potential Drought. Of the 2% of sites that are classified as Normal using the 1 month SPI index, all 18 fall into the Potential Drought category, when the longer 12 month SPI index is used. This indicates that on average the precipitation has been lower than average for the last 12 months at these sites. This is important, as many of our smaller groundwater abstractions can take significant periods of time to recharge after drought events. 6 Irish Water Specific Usage Prohibitions National Public Water Supply (excluding GDWSA)

9 Figure 4 National Overview 1 month SPI Index Summary: On review of Met Éireann forecasts and drought triggers developed as part of the draft Drought Management Plan, evidence of Drought has been established nationally. 7 Irish Water Specific Usage Prohibitions National Public Water Supply (excluding GDWSA)

10 2.2 Supply Side Pressures Irish Water abstracts raw water from over 1,200 individual water sources, including lakes, rivers, streams, springs and groundwater aquifers. All of these sources are reliant on sufficient rainfall to recharge. The relatively high temperatures that have accompanied this drought period have meant that rates of evaporation at surface water sites have increased, and the soil moisture deficit nationally ranges from -45 to -88 mm. Soil moisture deficit is the difference between the amount of water actually in the soil and the amount of water the soil can hold. This means that significant amounts of rainfall are required before water levels begin to recover the rivers, lakes and aquifers from which we abstract water for the public water supply. Figure 5, shows the soil moisture deficit for the Island of Ireland. Figure 5 Soil Moisture Deficit Met Éireann 3 rd July Irish Water Specific Usage Prohibitions National Public Water Supply (excluding GDWSA)

11 2.2.1 Surface Water Supplies For the surface water abstractions, individual catchment characteristics and regional climatic conditions give rise to a pattern of flows that varies from location to location. In practice this variation in flow is documented using a graphical representation known as a Flow Duration Curve (FDC). The FDC describes the percentage of time that observed flow in a river is likely to equal or exceed a specific flow value. For example, the 95th percentile flow, denoted Q95, is the flow rate equaled or exceeded 95% of the time at that site. Therefore, flows below Q95, are potentially indicative of the low flow events that would occur during a drought period. Figure 6 provides example FDCs for a variety of catchment types. The FDCs below have been modified by dividing values by the mean flow in the catchment to allow a like-for-like comparison of flow profiles for different catchment types. The 95% flow is a very important metric in terms water supply and wastewater treatment, as many of our water abstraction and wastewater discharges are based on the calculations of water availability and assimilative capacity at this flow. Figure 6 Sample Flow duration Curves (draft National Water Resources Plan) In order to assess our current position nationally, in terms of water levels and available flows, we are using EPA gauge data to plot our current position in relation to the FDCs and using recent flow records for monitoring locations around the country. Figure 7 shows a FDC for the EPA gauging station at Rathdrum, in Co. Wicklow. As can be seen from the graph, the gauge data shows that the current 9 Irish Water Specific Usage Prohibitions National Public Water Supply (excluding GDWSA)

12 flows at the gauge, on the 27 th of June were just above the Q95 flow for the river, i.e. entering low flow conditions. Q95 Figure 7 Flow Duration Curve Rathdrum 10 Irish Water Specific Usage Prohibitions National Public Water Supply (excluding GDWSA)

13 Figure 8 Flow Profile Rathdrum Also, of importance at this site, is the comparison between current water levels and expected water levels for this time of year. Normally low flow conditions occur towards the start of autumn, where baseflows have depleted over the course of the summer. As can be seen from Figure 8, for the Rathdrum gauge station, levels are approaching the lowest levels on record for this time of year. Therefore, water levels are likely to reduce further over the course of the summer. This demonstrates the need to suppress demand, in order to reduce unnecessary water use, and where possible contain the impacts of abstraction on the current water sources as much as possible. This is required to ensure the continued long term supply of water until winter. 11 Irish Water Specific Usage Prohibitions National Public Water Supply (excluding GDWSA)

14 Figures 9 and 10 show the current flows at the OPW gauge at Charleville, representative of sources in Co Louth. As at 3 July flows are at Q97, and again approaching the lowest levels for the time of year. Q95 Figure 9 Flow Duration Curve Charleville Figure 10 Flow Profile Charleville 12 Irish Water Specific Usage Prohibitions National Public Water Supply (excluding GDWSA)

15 Figures 11 and 12 show the current flows at the OPW gauge at Rathkennan in Co Tipperary. As at 3 July flows are at Q98, and again approaching the lowest levels for the time of year. Figure 11 Flow Duration Curve Rathkennan Q95 Figure 12 Flow Profile Rathkennan 13 Irish Water Specific Usage Prohibitions National Public Water Supply (excluding GDWSA)

16 Figure 13 depicts the latest 3 month hydrograph for Clifden Co Galway. Clifden has been used as a donor site to inform Irish Water estimates of Q95 flow at 13 surface water abstractions nationally, on the basis of similar catchment characteristics using standard estimation techniques. The Clifden gauge has been used as it is representative of the catchment conditions at the target sites. The plots below show that current flows 0.051m3/s at Clifden are below the Q95 flow value of 0.079m3/s. Figure 13 Flow Profile (Clifden, Co Galway) 14 Irish Water Specific Usage Prohibitions National Public Water Supply (excluding GDWSA)

17 Similarly at Coomhola in Co Cork, the EPA gauge has been used to inform flow estimates 22 abstraction sites nationally. Current flows at this gauge are 0.262m3/s which are very close to the estimated Q95 of 0.214m3/s. Figure 14 Flow Profile (Coomhola, Co Cork) In Virginia the OPW gauge (07033) on the Blackwater (Kells) has been used to estimate Q95 flows at 7 surface water abstractions nationally. Current measurements of flow at this gauge are 0.089m3/s which is well below the Q95 estimate of 0.15m3/s. Based on the evidence, and Irish Waters experience and expertise in water resource and drought management, it is difficult to avoid the conclusion that at least 42 surface abstractions nationally are likely to be abstracting from rivers flowing at close to, or less than 95 th percentile flow rates. 15 Irish Water Specific Usage Prohibitions National Public Water Supply (excluding GDWSA)

18 2.2.2 Ground Water Supplies Groundwater sources supply 17% percent of our total water supply, either from boreholes, springs or infiltration galleries. Ireland s bedrock is hard and fractured. In most of the country it is possible to get enough water for a domestic water supply. Therefore, all of the country s bedrock is classified as an aquifer. However, most of the bedrock is relatively poor at storing and transmitting groundwater. The majority of Ireland is occupied by poorly productive aquifers, meaning large rates of abstraction at a single point are often impossible. The bedrock is covered by different types of subsoil of varying degrees of thickness. This subsoil helps protect groundwater and is a controlling factor on the amount of recharge that gets to the groundwater from the rainfall that falls on the land surface. Climate is another controlling factor on recharge rates, and the effective rainfall greatly reduces from west to east across the country. The current drought conditions, will affect recharge rates at all of our groundwater abstractions, and soil moisture deficits above these aquifers mean that significant amounts of rainfall will be required to replenish current supply sources. As these water sources are slow to recover, effects of the current drought may impact these sources for a 12 month period. It is therefore imperative that we do not over abstract water for non-essential purposes at these sites during this period. Figure 15 Borehole water levels Ballydavis Portlaoise Figure 15, shows level data from one of our boreholes, in the highly productive karst limestone aquifer in Portlaoise. The wellfield in the region supports a population of 28,000 via ten boreholes, supplying an average of 11.5 Ml/d. Portlaoise was chosen for the purposes of this report on the basis that it is one of Irish Waters most significant groundwater sources. 16 Irish Water Specific Usage Prohibitions National Public Water Supply (excluding GDWSA)

19 For a borehole well, in normal conditions the abstraction rate would not be above the recharge rates, and therefore aside from daily fluctuations based on pumping, the well level would remain relatively static. As can be seen from Figure 15, the water levels in the well are reducing due to a combination of drought conditions affecting recharge and increased demands. In summary, our supplies are currently under significant pressure, due to the following: High temperatures are resulting in increased evaporation at surface water sites Soil moisture deficits are affecting groundwater and surface water recharge rates Due to Soil Moisture Deficits and the low water levels in rivers, lakes and streams, it may take many months for raw water sources to recover and recharge to normal levels For groundwater supplies, as these water sources are slow to recover, effects of the current drought or near drought conditions may impact these sources for a 12 month period. Many water bodies support multiple pressures (both abstractions & discharges), including those for agricultural and other purposes such that a focus on individual water schemes within particular regions does not address the holistic environment of the waterbody Lower flowrates in rivers and longer residence times in lakes is putting increased environmental stress on water bodies, impacting the assimilative capacity of these water bodies to cope with wastewater and other discharges, this has increased risks to the aquatic environment and ecology Summary: Evidence of the current vulnerability of a representative sample of our current water supply sources has been established. 17 Irish Water Specific Usage Prohibitions National Public Water Supply (excluding GDWSA)

20 2.3 Increased Demand for Water The average demand for water in the public water supply nationally, for 2018 is 1,650 Ml/d. Over the past ten days, demand for water on our network has increased by an average of 15% to 1,900 Ml/d. Average Demand Peak Demand % increase GDWSA % Nationally outside GDWSA % Overall Nationally % Table 3 Demand increases Figure 16 Representitive sample of Demand Increase Nationally This quantity of water is above the sustainable water supply volume for the majority of our existing sites and large scale water restrictions and outages are inevitable if demand is not reduced through voluntary reductions or restrictions in water usage. 18 Irish Water Specific Usage Prohibitions National Public Water Supply (excluding GDWSA)

21 Figure 16, highlights the sites where demand is currently above sustainable production levels, At these locations, Irish Water is currently suppressing network pressure, and restricting demand at twenty eight supplies. At eighteen of these locations we are also tankering in water to the supply reservoirs in order to meet demand. Night-time restrictions are being put in place to allow reservoirs to recover and ensure demand is met throughout the day. 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 2017 was 1,680 Ml/d, this dropped to 1,650 Ml/d for the first months of 2018, however, demand has increased nationally to 1,900 Ml/d over the past two weeks. This level of demand is unsustainable, even in the short term, and unless it can be reduced significantly water supplies may be at risk of significant restrictions or outages until the end of the 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 nationally, with additional crews deployed since Monday the 25 th of June. Enhanced pressure management and night time water restrictions have been in place in some areas 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 approaching maximum sustainable production levels Irish Water is currently relying on tankering to support smaller local reservoirs and is concerned that it may need to meet increased agricultural demand as private sources come under pressure 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; demand is still increasing. Irish Water made an Order on 2 nd July prohibiting certain non-essential water uses in the Greater Dublin Water Supply Region, up until 31 st July. 19 Irish Water Specific Usage Prohibitions National Public Water Supply (excluding GDWSA)

22 Summary: Irish Water has exhausted all measures to increase supply and reduce demand, voluntarily and without impacting customers 4. Additional Actions Required Prior to the making of the Order dated 2 nd July 2018 in relation to the Greater Dublin Water Supply Area, Irish Water has attempted to reduce 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 country. 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 nonessential 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 that this is the first time such restrictions will have been used nationally, 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. Similar restrictions imposed in the Greater Dublin Water Supply Area on the 2 nd of July 2018, appear to be successfully suppressing demand by about 3%. 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, 20 Irish Water Specific Usage Prohibitions National Public Water Supply (excluding GDWSA)

23 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 specific any notice period. Having regard to this, a reasonable notice period will be given. The notice period must also give consideration to the extent of the drought problem, the restriction of non-essential activities, and the fact that unless this action is taken and 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 country. 5. Conclusion and Recommendation The national public water supply is at risk due to current drought conditions that are placing existing water supplies at risk whilst causing unprecedented increases in demand for water. Met Eireann 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. 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/or 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 national 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). 21 Irish Water Specific Usage Prohibitions National Public Water Supply (excluding GDWSA)

24 To introduce these prohibitions in all areas of the Public Water Supply network, excluding the Greater Dublin Water Supply Area, where an order prohibiting non-essential water use until 31 st July 2018 is already in place since the 2 nd of July Irish Water Specific Usage Prohibitions National Public Water Supply (excluding GDWSA)

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