Vision The resilience of water supply and sanitation in the face of climate change. Technology fact sheets

Transcription

1 Vision 2030 The resilience of water supply and sanitation in the face of climate change Technology fact sheets

2 Authors: Dr Katrina Charles, Robens Centre for Public and Environmental Health, University of Surrey Dr Kathy Pond, Robens Centre for Public and Environmental Health, University of Surrey Dr Steve Pedley, Robens Centre for Public and Environmental Health, University of Surrey Contributors: The authors would like to thank the following individuals who participated in a working session to define climate risks and technology vulnerabilities and adaptations: Mr Chee-Keong Chew, Water, Sanitation, Hygiene and Health, World Health Organization Dr Barbara Evans, Water and Environment, University of Leeds Professor Barry Lloyd, Centre for Environmental Health Engineering, University of Surrey Mr Brian Reed, Water, Engineering and Development Centre, Loughborough University Ms Beth Scott, Policy and Research Division, Department for International Development Professor Mike Smith, Water, Engineering and Development Centre, Loughborough University Dr David Sutherland, Principal Consultant, Atkins Dr Richard Taylor, Department of Geography, University College London Disclaimer The fact sheets were prepared in good faith. The named authors alone are responsible for the views expressed in this publication. Neither the World Health Organization and University of Surrey, UK, nor their employees, contractors or subcontractors, make any warranty, express or implied, or assume any legal liability or responsibility for its accuracy, completeness, or any party s use of its contents. The fact sheets are not edited by the World Health Organization to conform to the full requirements of WHO style. The published material is being distributed without warranty of any kind, either expressed or implied. The responsibility for the interpretation and use of the material lies with the reader. In no event shall the World Health Organization be liable for damages arising from its use.

3 Introduction The Technology projection study (included in this CD-ROM) discusses a number of themes related to climate change, and in particular describes the consequential changes in rainfall patterns, and the observed and perceived impact of these changes on drinking-water supply and sanitation facilities. The evidence gathered from the literature, and from the opinions and experiences of experts working in the field, demonstrates the vulnerability of drinking-water supply and sanitation facilities, at all levels of sophistication, to the vagaries of the present climate. These observations suggest that without intervention, the vulnerability of these facilities to climate-induced damage will increase in the future as climate conditions become more extreme. This assumption is supported by the opinions of many of those working in the water and sanitation sector. The evidence gathered in preparing that report also showed that there are interventions that can be made to reduce the vulnerability of drinking-water supply and sanitation facilities to climate change. Several examples of successful adaptation were noted. Based on the positive results of those interventions and the opinions of water and sanitation professionals, we have compiled a series of fact sheets containing guidance about the kind of interventions that may be considered suitable for increasing the resilience of drinking-water supply and sanitation facilities to the consequences of several climate-change scenarios. These notes should not be considered a complete authoritative guide to the interventions that can be made to protect these facilities from climate change. The impacts of changing patterns of rainfall are many and varied, and will be conditional on the local environment. Similar scenarios, therefore, will have different consequences depending on where they occur. These guidance notes provide a first attempt at presenting a framework for adaptation in the water supply and sanitation sector and, as such, they are intended to raise awareness of the potential problems that will be faced in the short to medium term in the water and sanitation sector. Their contents are not fixed but will change and grow over time as new knowledge and experience are added to them. Most of all, however, the guidance notes are intended to promote debate in the water and sanitation sector. The intended users of these guidance notes are water supply and sanitation professionals, water resource managers, public health professionals, communities managing their own water supplies, and nongovernmental organizations working in the water supply and sanitation sector. Four climate scenarios are addressed in these vulnerability and adaptation guidance notes: increase in precipitation, with increase in rainfall intensity; increase in precipitation, with no increase in rainfall intensity; decrease in precipitation, with increase in rainfall intensity; decrease in precipitation, with no increase in rainfall intensity. The fact sheets are divided up by key issues for water supply and sanitation facilities as a result of these four climate scenarios. The relevant key issues for each scenario are indicated in Table 1. The adaptations have been divided into four categories: capital expenditure, which includes long-term adaptations that will not necessarily be suitable for immediate implementation; operational expenditure, which includes adaptations that can be made to existing systems; monitoring, which includes programmes that can be implemented immediately to support planning decisions, or implemented in the long term to support continuing decisions; Socioeconomic tools such as community education, training and public awareness that can support short-term and long-term adaptations.

4 Table 1 Summary of problems relating to climate change for four different scenarios Key issues Scenario Increase in precipitation, increase in rainfall intensity Increase in precipitation, no increase in rainfall intensity Decrease in precipitation, increase in rainfall intensity Increased risk of flooding Increase in groundwater recharge, with a rise in groundwater level, increases in interflow and more saturated soils More extreme rainfall events Increased run-off with more erosion Water availability decreases including less surface flow, drop in surface water levels, and decreased groundwater levels Decrease in precipitation, no increase in rainfall intensity In all cases we refer the reader to the Water Safety Plan approach as a means of consistently ensuring the safety of a drinking-water supply. Model water safety plans for the water facilities referred to below are provided in The water supply and sanitation facilities discussed in these fact sheets are those defined as improved by the WHO/UNICEF Joint Monitoring Programme on Water Supply and Sanitation (see Table 2). Levels of coverage are discussed in Chapter 4 of the Technology projection study, based on data from the WHO/UNICEF Joint Monitoring Programme. The fact sheets provide guidance with regard to vulnerability and adaptation of water supply and sanitation facilities to the effects of climate change. They deal with the following key themes: Water supply Flooding increases Groundwater recharge increases Increase in extreme rainfall events Run-off increases Water availability decreases Sanitation Flooding increases; increase in extreme rainfall events Groundwater tables rising Water availability decreases.

5 Table 2 Definitions of improved water supply and sanitation facilities Water supply or sanitation facility Utility-managed piped water supplies Community-managed drinkingwater systems Public standpipes Protected wells Protected springs Rainwater collection Sewers Septic tanks Improved pit latrines Composting or dry latrines Notes or definition May have either a surface water or groundwater source, and include infrastructure such as a reservoir and a treatment plant, with treated water delivered to users via a piped network. These may be with piped or non-piped distribution. The definition of a community drinking-water system will vary. It may be based on population size or the type of supply; or based on the approaches to administration and management. Drinking-water systems in periurban areas in developing countries the communities surrounding major towns and cities may also have the characteristics of community systems. Standpipes deliver water supplied by a utility or community managed supply, and hence have the same vulnerabilities as one of those systems. However, with public standpipes, the water is not delivered to the consumers, but to a tap or standpipe for which there is public access. Includes boreholes and dug wells. A protected spring is one in which the eye of the spring (where the water emerges from the ground) has a protective wall or box around it. The area behind the box is backfilled with stones to filter the groundwater. Collection of rainwater from roofs: rainwater is collected in guttering placed around the eaves of the building. Sewer systems collect all household wastewater, as well as industrial and commercial wastewater, and transport it via a network of sewerage pipes to a central treatment or disposal site. Combined sewer systems are included in the definition of sewers. Septic tanks collect all household wastewater, and should collect only wastewater, not storm water. Includes pour-flush latrine, and simple (or double) pit or ventilated improved pit latrine, allowing for acceptable local technologies. Composting or dry latrines are constructed with the collection chamber for faeces (and urine) above ground. The position of the collection chamber facilitates drying of the contents and easy access for its removal.

6 Key issue: Flooding increases Utility-managed piped water supplies Increased flooding reduces the availability of safe water resources. Flooding events increase the level of chemical and microbiological contamination in water sources, increasing the risk to public health. Increased suspended sediment load carried by flood waters exceeds the treatment capacity of water treatment facilities. Develop, implement and Seasonal forecasting. Hydrological monitoring update water safety plans. stations. Design flood storage areas on rivers to mitigate the impacts of floods. This may include implementing land management activities to increase infiltration of water and reduce severity of floods, e.g. terracing, adequate urban drainage, reforestation, retention basins. Adopt higher design standards for infrastructure to take higher and more frequent floods into consideration, particularly in terms of return periods for significant events. Best management practices (grass swales, permeable surfaces, balancing ponds). Flood forecasting. Rain gauging. Earth observation data. Enhanced inspection of infrastructure. the public of the risk of contamination during floods and the reduction in drinking-water availability. Dissemination of public health advisory notices with advice about dealing with the issues. Possible mechanisms include posting leaflets, door-to-door visits, and radio and television announcements. Fluctuating surface water levels may cause problems for infrastructure Water intakes may be left exposed as water levels fall. Develop, implement and update water safety plans. Design water intake to Switch to groundwater sources when available. Repair damage as Hydrological monitoring stations. Rain gauging. Earth observation data. operational managers of the need for enhanced inspection procedures.

7 Highly turbulent water flows in rivers after heavy rain may damage intakes. accommodate varying water necessary. Enhanced inspection of levels (for example floating infrastructure Communicate the booms). River intakes Plan for emergency water justification for enhanced strengthened to withstand supplies. inspection as a result of more turbulent flows. climate change. Develop groundwater sources where feasible. Floods may overtop reservoir causing structural damage Catastrophic failure of dams, leading to reduced storage capacity and potentially damaging releases of water. Design overflows for source reservoirs to prevent failure Maintain spillways and channels in good order. Early warning system installed. Disseminate early warnings. Update and disseminate evacuation procedures. Increase frequency with which emergency procedures are practised. Flooding of treatment system Floods may lead to structural damage of the treatment works, or to the failure of pumping stations. Water supplies fail. Develop, implement and update water safety plans. Site water treatment works and other major infrastructure away from flood zones, or build appropriate flood defences. Protect electrical installations. Smaller more localized treatment systems may help to spread risk of widespread water shortages. Plan after-flooding response to assess and address infrastructure damage. Take treatment unit offline and apply corrective action. Planned emergency response. Increase chlorination. Plan for emergency supplies. Intensify monitoring of water quality after event and before going back on line. Manage communication of early warning of event to the public. Develop communication procedures for notifying the public when the water is safe. Possible mechanisms include posting leaflets, door-todoor visits, and radio and television announcements. water engineers of risks

8 from water quality changes during flooding and how water treatment can be adapted to manage the risks. Groundwater quality deterioration during floods Floodwaters contaminate shallow and deep groundwater sources through damaged or disused boreholes. Shallow groundwater may also be affected by infiltration of flood water through soil layers. Develop, implement and update water safety plans. Improve source protection. Introduce chlorination where not previously applied. Relocate groundwater source. Impose well head protection areas and well head inspection procedures. Increase chlorination of the water after flood. Intensify water quality monitoring after flood. water engineers of risks from water quality changes during flooding and how water treatment can be adapted to manage the risks. Manage communication of early warning of event to the public. Develop communication procedures for when water is safe. Possible mechanisms include posting leaflets, door-todoor visits, and radio and television announcements. Surface water quality deterioration during floods. Floodwater carries increased sediment load that may exceed the treatment capacity of the water treatment works. Run-off water from upstream may carry Develop, implement and update water safety plans. Adapt water treatment for flood conditions depending on water source and contamination. Select appropriate water treatment stages to suit water quality. Dig out buried intakes after flood waters recede. Design and implement a monitoring programme of flooding in water sources. Monitor silt build-up in reservoirs. water engineers of risks from water quality changes during flooding and how water treatment can be adapted to manage the risks.

9 higher concentrations of chemical and microbial contaminants. Introduce additional, more Monitor raw water Manage communication robust barriers and treatment quality. of early warning of event stages. to the public. Relocate abstraction points. Develop communication procedures for when water is safe. Possible mechanisms include posting leaflets, door-todoor visits, and radio and television announcements. Entry of contaminated flood water into water supply pipes. Localized or widespread contamination of the water distribution system. Develop, implement and update water safety plans. Where possible, aim to site pipes in area of low risk of flooding. In areas where flooding is likely, aim to keep water and sewage pipes separate in case of cross contamination through fractures. Relocate water pipes away from open sewers and drainage channels. Implement pipe maintenance programme to reduce leakage and the potential for ingress. Implement pipe maintenance programme to reduce leaks from sewers, particularly where located close to water pipes and where cross connection is possible. Include cut-off walls in high-risk areas. Implement rehabilitation programmes to improve hydrostatic pressure. Design and implement a monitoring programme for flooding of the pipe network. This might include monitoring of water pressure in pipes, water quality monitoring, or a reporting mechanism for when areas above pipes are flooded. Review risks and need for refurbishment or replacement. st the public of contamination issues during floods and reduction in drinkingwater availability. This may be done by posting leaflets, door-to-door visits; radio and TV announcements to inform people to boil water. Flush out flooded pipe network after waters have receded to remove sediments. Shock

10 chlorinate the system and introduce increased chlorination until risk of contamination has been reduced. Entry of contaminated water at service reservoir. Localized or widespread contamination of the water distribution system. Develop, implement and update water safety plans. Re-line reservoirs. Re-point concrete reservoirs. Replace or repair damaged access points to the service reservoir. Clear drainage channels. Take tanks offline for repairs. Flush tank and distribution before re-commissioning. Repair leaks, drains and valve box. Repair valve if showing signs of wear Validation by water quality monitoring at times of major works. Regular inspection. Periodic integrity testing. Tracer tests. the public of contamination issues during floods and reduction in drinkingwater availability. This may be done by posting leaflets, door-to-door visits, and radio and television announcements to inform people to boil water. Contamination of drinking-water in supply affecting large populations. Major public health risk. Develop, implement and update water safety plans. Decentralize and diversify water systems to mitigate the number of people affected. Develop back-up sources, such as linkages to other sources or emergency tank supplies, to mitigate risk. Zoning of water supplies for monitoring and management of distribution system. Implement leak detection and repair procedures. Intensification of water quality monitoring above minimum level specified in WHO guidelines. the public of contamination issues during floods and reduction in drinkingwater availability. This may be done by posting leaflets, door-to-door visits, and radio and television announcements. Establish communication procedures with the relevant public health departments.

11 May also require the issue of warnings to boil water. Enhance and practice emergency response procedures. Flooding causes damage to bridges that support trunk mains or distribution pipes over rivers. Localized or widespread disruption to water supplies. Develop, implement and update water safety plans. Review relative risks and the cost-benefits of laying the trunk main under the river or supporting from bridge over the river. Select most costbeneficial option. Carry out regular inspection and vulnerability assessment of structures. Develop monitoring, management and communication procedures with the bridge owners, if different from water supply provider. Install multiple crossings for distribution pipes. Install isolation valves at both sides of crossing. Community-managed piped water supplies Increased flooding reduces the availability of safe water resources. Flooding events increase the level of chemical and microbiological contamination in water sources, increasing the risk to public health. Develop, implement and Seasonal forecasting. Hydrological monitoring update water safety plans. stations. Adopt higher design standards for infrastructure to take Flood forecasting. Establish centralized support unit to provide Enhanced inspection of infrastructure. the community of the risk of contamination during floods and reduction in drinkingwater availability.

12 Increased suspended sediment loads carried by flood waters may exceed the treatment capacity of any smallscale water treatment system that has been added to the supply. higher and more frequent technical and floods into consideration, administrative assistance particularly in terms of in the event of flooding return periods for significant events. Where possible, implement land management activities to increase infiltration of water and reduce severity of floods, e.g. terracing, reforestation. Dissemination of public health messages with advice about dealing with the issues, including household treatment and boil water notices where appropriate. This may be done by posting leaflets, door-to-door visits, radio and television announcements, and by posting notices in prominent places in the community. Fluctuating surface water levels may cause problems for infrastructure. Water intakes may be left exposed as water levels fall. Highly turbulent water flows in rivers after heavy rain may damage intakes. Develop, implement and update water safety plans. Strengthen river intakes to withstand more turbulent flows. Develop groundwater sources where feasible. Establish centralized support unit to provide technical and administrative assistance in the event of flooding. Switch to alternative sources when available. Repair damage as necessary. Hydrological monitoring stations. Enhanced inspection of infrastructure community members of the need for enhanced inspection procedures. Communicate the justification for enhanced inspection as a result of climate change. Plan for emergency water supplies. Floods may overtop reservoir causing structural damage. Catastrophic failure of the dam, leading to reduced storage capacity Design overflows for source reservoirs to prevent failure. Maintain spillways and channels in good order. Evaluate need for early warning system. Disseminate early warnings.

13 and potentially damaging releases of water. Evaluate the need for evacuation procedures. Increase frequency with which emergency procedures are practised if appropriate. Flooding of water treatment system. Distribution of contaminated water through the distribution system. Water supplies fail. Structural damage to the treatment system. Develop, implement and update water safety plans. Site the water treatment works and other major infrastructure away from flood zones, or build appropriate flood defences. Protect electrical installations, e.g. with walled treatment plant or sandbag defences. Establish centralized support unit to provide technical and administrative assistance in the event of flooding. Plan after-flooding response to assess and address infrastructure damage. Take treatment unit offline and apply corrective action. Planned emergency response. Increase chlorination. Plan for emergency supplies. Sanitary inspection. Increase monitoring of water quality after event and before going back on line, possibly using external support systems. Manage communication of early warning of event. Develop communication procedures for when water is safe. Raise awareness of risks from water quality changes during flooding Raise awareness about risks from infrastructure damage after flooding and how to assess and address them. Raise awareness of the need for household water treatment. Groundwater quality deterioration during floods. Floodwaters contaminate shallow and deep groundwater sources through damaged or disused boreholes. Develop, implement and update water safety plans. Improve source protection. Impose well head protection areas and well head inspection. Sanitary inspection. Intensify water quality monitoring after flood. Develop communication procedures for when water is safe.

14 Shallow groundwater may also be affected by infiltration of floodwater through soil layers. Risk to public health from consuming the water. Relocate groundwater Shock chlorination after Raise awareness about source where possible. flood. risks from water quality changes during flooding and the need for household water treatment. Possible mechanisms include posting leaflets, door-todoor visits, radio and television announcements, and positing notices in prominent places in the community Surface water quality deterioration during floods. Floodwater carries increase sediment load that may exceed the treatment capacity of any small-scale water treatment system that is part of the supply system. Run off water from upstream may carry higher concentrations of chemical and microbial contaminants. Risk to public health from consuming the water. Develop, implement and update water safety plans. Adapt water treatment for flood conditions depending on water source and contamination. Introduce additional more robust barriers and treatment stages. Relocate abstraction points, where possible. Select appropriate water treatment stages to suit water quality. Dig out buried intakes after the flood waters recede. Sanitary inspection. Simple monitoring of raw water quality, e.g. turbidity. Develop communication procedures for when water is safe. Raise awareness about risks from water quality changes during flooding and the need for household water treatment. Possible mechanisms include posting leaflets, door-todoor visits, radio and television announcements, and posting notices in prominent places in the community.

15 Issue boil water notices where appropriate. Entry of contaminated flood water into water supply pipes. Widespread contamination of the water supply system. Risk to public health from consuming the water. Develop, implement and update water safety plans. Aim to site pipes in area of low risk of flooding. Relocate water pipes away from open sewers and drainage channels. Introduce a pipe maintenance programme to reduce leakage and potential for ingress, possibly with the aid of a central support system. Rehabilitation to improve hydrostatic pressure. Flush out flooded pipe network after waters have receded to remove sediments. Shock chlorination. Sanitary inspection. Develop and implement reporting mechanism when areas above pipes are flooded. Review risks and need for refurbishment or replacement. Raise awareness about risks from water quality changes during flooding and the need for household water treatment. This may be done by posting leaflets, door-to-door visits, radio and television announcements, and posting notices in prominent places in the community. Issue boil water notices where appropriate. Develop communication procedures for when water is safe Contamination of drinking-water in supply affecting whole community. Severe risk to public health from consuming the water. Develop, implement and update water safety plans. Develop back-up sources, such as linkages to other water sources or community water supply systems. Develop emergency backup supplies. Regular programme of leak detection and repair. Sanitary inspection. Raise awareness about risks from water quality changes during flooding and the need for household water treatment Issue boil water notices where appropriate.

16 Develop communication procedures for when water is safe This may be done by posting leaflets, door-todoor visits, radio and television announcements, and posting notices in prominent places in the community. Enhance and practise emergency response procedures. Flooding causes damage to bridges that support mains or distribution pipes over rivers. Localized or widespread disruption to water supplies. Develop, implement and update water safety plans. Review risks and benefits of burying main under river or supporting from bridge over the river. Select least risk option. Carry out regular inspection and vulnerability assessment of structures. Develop monitoring, management and communication procedures with the bridge owners, if not owned by the community. Install isolation valves at both sides of crossing.

17 Public standpipes See also utility- and community-managed piped water supplies Standpipes inundated with contaminated floodwater. Develop, implement and update water safety plans. Sanitary inspection of standpipe. Standpipes become inaccessible or are damaged by the floodwater. Quality of the water at the standpipe deteriorates and there is potential for more widespread contamination of the distribution system. Place on elevated platform to allow access during floods. Construct standpipes from durable materials to reduce damage during floods. Review the risks and benefits of removing the standpipe if it is located in an area at high risk of flooding. Adopt a standpipe maintenance programme to reduce potential for ingress (e.g. chambers are sealed). Develop response plan after flooding to assess damage to standpipes and to inform future improvement. Flush out pipes and clean standpipes after floods. Increase water quality monitoring after floods have receded. Raise awareness about risks from water quality changes during flooding and the need for household water treatment. Issue boil water notices where appropriate. Develop communication procedures for when water is safe. This may be done by posting leaflets, door-todoor visits, radio and television announcements, and posting notices in prominent places in the community. Protected wells (boreholes and dug wells) Increased contamination of groundwater and lateral flow in soil. Floodwaters introduce contamination into the groundwater by Site well away from Repair rendering of well Sanitary inspection. Prevent latrines being latrines and other wall when necessary. constructed nearby. sources of groundwater Monitor the response of

18 infiltration though the soil, by damaged or disused bore holes or dug wells. Lateral flow increases, transporting contaminants below the surface. Significant public health risks from consuming the water. pollution. groundwater levels and Raise awareness about quality to flooding, to risks from water quality identify vulnerability. changes during flooding and the need for household water treatment. Issue boil water notices where appropriate. Develop communication procedures for when water is safe. This may be done by adding warning labels to contaminated wells and boreholes and removing the notices when the water is safe. In areas where there is a high density of boreholes and dug wells, consider developing an association of well owners and stakeholders to manage and monitor wells and provide guidance to users. Raise awareness of well use in emergency situations.

19 Well is inundated. Widespread contamination of the aquifer, causing longterm problems with the quality of water in the well. Significant public health risks from consuming the water. Build bunds (banks, Repair and clear ditches. Sanitary inspection. dykes or levees) to divert flow, or raise the well Increase size of ditch. Increase water quality head. monitoring. Site on embankments. For deep wells, ensure the casing extends below the level of shallow aquifers. Extend lining above ground. Convert dug wells to hand pumped tubewells with sanitary completion. Improve well lining to prevent ingress of water from soil and shallow groundwater, where appropriate. Implement land management activities to reduce severity of floods, e.g. terracing, adequate drainage, reforestation, retention basins. Repair plinth. Shock chlorinate well water after the floods have subsided. Provision of alternative water sources during inundation or household treatment. Monitor conductivity if in coastal or estuarine areas. Raise awareness about risks from water quality changes during and after flooding, and the need for household water treatment. Issue boil water notices where appropriate. Develop communication procedures for when water is safe. This may be done by adding warning labels to contaminated wells and boreholes and removing the notices when the water is safe. In areas where there is a high density of boreholes and dug wells, consider developing an association of well owners and stakeholders to manage and monitor wells and provide guidance to users. Raise awareness of well use in emergency situations.

20 Prepare flood risk map and update as necessary. Protected springs Entry of contaminated surface water at the spring. Erosion around the spring box, damaging protection. Quality of water from the spring deteriorates. Water quality changes may be rapid but shortterm if contamination enters at the spring. Significant public health risks from consuming the water. Ensure spring water Regularly check the Sanitary inspection. collection and storage infrastructure and repair users about risks from infrastructure are if necessary. water quality changes properly designed, during and after flooding protected and maintained Maintain surface water and the need for to prevent entry of diversion ditch above household water contaminated water, and and around spring. treatment. are constructed from durable materials. Build bunds (banks, dykes or levees) and cutoff drains to divert flow away from collection area. Advise community to avoid using contaminated springs for drinking during and after floods, until quality has been verified. Issue boil water notices where appropriate. Develop communication procedures for when water is safe. Groundwater quality deteriorates. Quality of the water from the spring deteriorates. Water Investigate alternative sources if appropriate and possible. Properly seal abandoned wells to protect groundwater quality. Water quality monitoring after a flood to verify that water Advise community to avoid using contaminated springs for

21 quality changes may be long-term if the aquifer becomes contaminated. quality is not compromised. Maintain well head or spring head protection areas. drinking during and after floods, until quality has been verified. users about possible contamination of the aquifer following floods, irrespective of localised flooding at the collection area. Flooding reducing availability of safe water. Eye of the spring submerged under floodwater. No access to water source. Develop springs outside flood prone areas, where possible. Implement land management activities to reduce severity of floods, e.g. terracing, adequate drainage, reforestation, retention basins. users of potential consequences of flooding on the quality of water and actions to be taken in such circumstances. Prepare flood risk map and update as necessary. Investigate alternative sources.

22 Rainwater collection Collection or storage facilities are inundated. Rainwater collection or storage systems become inaccessible. Introduction of contamination into the rainwater storage system. Avoid using Clean and disinfect all Sanitary inspection. underground storage storage and collection the users about possible facilities in flood prone facilities, after Monitor for microbial contamination of the areas, and ensure proper inundation in flood contamination where system following floods, design and maintenance water, before use. possible. including contamination of all storage and of the stored water. collection facilities to Strengthen collection prevent contamination. and storage facilities. Raise level of storage tanks where possible. Consider accessibility issues when designing rainwater collection for an area to ensure that some supplies are accessible in floods. Consider increasing capacity. Investigate alternative sources. Plan for collection of increased silt load. Provide information about increased silt load and increased capacity.

23 Key issue: Groundwater recharge increases Utility-managed piped water supplies Potential deterioration in the quality of groundwater sources as a result of more rapid transport of water in subsurface, and potential compromising of sanitation systems. Increase vulnerability of flooding (see flooding). Rising groundwater levels flood sanitation systems, creating pathways for the potentially rapid dispersal of contaminants into groundwater. Rising water level mobilize microbial and chemical contaminants. Ingress of groundwater into treated water supply, potentially contaminating water. Significant public health risk from consuming the water. Develop, implement and Maintain positive update water safety pressure in pipes plans. wherever possible Investigate increasing protection zones around wells, to reduce contamination sources. Adapt water treatment to respond to changing water quality. Increase the depth of well intakes, where possible. Move towards continuous positive pressure in system. Investigate the benefits of placing increased reliance on groundwater systems in areas of rising groundwater, provided appropriate treatment can be added. Pipe maintenance programme to fix leaks in pipes. Design and implement a monitoring programme for groundwater sources based on groundwater level. Monitor the response of groundwater levels and quality to increasing rainfall, to identify vulnerability. Monitor water quality in at-risk pipe networks resource managers, water and sanitation professionals, public health professionals and consumers about possible groundwater contamination issues and health impacts. consumers of the need for household water treatment. Issue boil water notices when appropriate.

24 Community-managed piped water supplies Potential deterioration in the quality of groundwater sources as a result of more rapid transport of water in subsurface, and potential compromising of sanitation systems. Increase vulnerability of flooding (see flooding). Rising groundwater levels flood sanitation systems, creating pathways for the potentially rapid dispersal of contaminants into groundwater. Rising water level mobilizes microbial and chemical contaminants. Ingress of groundwater into treated water supply, potentially contaminating water. Significant public health risk from consuming the water. Investigate increasing Establish centralized Design and implement a protection zones around support unit to provide monitoring programme the community of the wells, to reduce technical and for groundwater sources risk of contamination contamination sources. administrative based on groundwater from rising. assistance. level. Adapt water treatment to respond to changing water quality. Develop, implement and update water safety plans. Investigate the benefits of placing increased reliance on groundwater systems in areas of rising groundwater, provided appropriate treatment can be added. Increase the depth of well intakes, where possible. Move towards continuous positive pressure in system. Maintain positive pressure in pipes wherever possible. Pipe maintenance programme to fix leaks in pipes. Monitor the response of groundwater levels and quality to increasing rainfall, to identify vulnerability. Sanitary inspection. Dissemination of public health messages with advice about dealing with the issues, including the need for household treatment and boil water notices where appropriate. This may be done by posting leaflets, door-todoor visits, radio and television announcements, and by posting notices in prominent places in the community.

25 Public standpipes See utility- and community- managed piped water supplies Protected wells (boreholes and dug wells) Potential deterioration in the quality of groundwater sources as a result of more rapid transport of water in subsurface, and potential compromising of sanitation systems. Significant risk to the health of consumers. Increase in groundwater level could also lead to a reduction in the vulnerability of protected wells and provide a more sustainable water supply than alternative water supply options. Investigate increasing Establish centralized Design and implement a Prevent latrines being protection zones around support unit to provide monitoring programme constructed nearby. wells, to reduce technical and for groundwater sources contamination sources. administrative based on groundwater assistance. level. Adapt water treatment to respond to changing water quality. Set intakes at greater depth or modify pumping regimes, where feasible. Act upon sanitary risk inspections. Monitor the response of groundwater levels and quality to increasing rainfall, to identify vulnerability Sanitary inspection. users of the wells about risks from water quality changes during flooding and the need for household water treatment. Issue boil water notices where appropriate. In the event of a decrease in the vulnerability of protected wells, an increase in the reliance on groundwater sources should be considered. Develop communication procedures for when water is safe. This may be done by adding warning labels to contaminated wells and boreholes and removing the notices when the water is safe. In areas where there is a high density of boreholes

26 and dug wells, consider developing an association of well owners and stakeholders to manage and monitor wells and provide guidance to users. Raise awareness of well use in emergency situations. Protected springs Increased flow of the spring may cause damage to the existing infrastructure. Spring protection damage, leading to increase vulnerability of the spring to ingress of surface contamination. Significant risk to the health of users of the spring. Investigate installing Repair structure and Sanitary inspection. Communicate risk to the additional drainage or reinforce as necessary to users of the spring. overflow pipes to reduce risks identified by Advise household alleviate pressure buildup. sanitary inspection. treatment as necessary. Design and construct spring box storage to account for increase flows. Establish centralized support unit to provide technical and administrative assistance. Potential deterioration in the quality of groundwater sources as a result of more rapid transport of water in subsurface, and potential compromising of sanitation systems. Significant risk to the health of users of the spring. Investigate increasing protection zones around source, to reduce contamination sources. Adapt water treatment to respond to changing water quality. Act upon sanitary risk inspections. Establish centralized support unit to provide technical and administrative assistance. Design and implement a monitoring programme for groundwater sources based on groundwater level. Monitor the response of spring discharges to users of the springs about risks from water quality changes and the need for household water treatment. This may be done by adding warning labels to

27 groundwater levels and contaminated springs quality to increasing and removing the notices rainfall, to identify when the water is safe. vulnerability. Sanitary inspection.

28 Key issue: Increase in extreme rainfall events One of the main impacts of more extreme rainfall events will be flooding, so these tables build on the vulnerabilities of general flooding with vulnerabilities associated with heavy rainfall and flash flooding. Utility-managed piped water supplies See also key issue: Flooding increases Damage to Potential failure of the infrastructure. drinking-water supply system and loss of service. Public health risk from contaminants entering the water distribution system through damaged pipes. Design or adapt reservoir overflows and spillways to cope with larger flows. Adopt higher design standards for infrastructure to take more frequent extreme weather events into consideration. Develop, implement and update water safety plans. Response plan after flooding to assess and address infrastructure damage. Plan for emergency supplies of drinkingwater to be available in the event of system failure. Hydrological monitoring stations. Rain gauging. Earth observation data. Enhanced inspection of infrastructure. the public of the risk of contamination during and after extreme rainfall events. water engineers of risks from water quality changes during extreme rainfall events, and how to manage the risk. Disseminate health advisory notices to the public with advice about dealing with the risks. Develop communication procedures to notify public when the water is safe. Issue boil water notices if appropriate. Possible mechanisms include posting leaflets,

29 door-to-door visits, and radio and television announcements. Treatment and pumping systems unable to work if electricity is affected. Potential failure of the drinking-water supply system and loss of service. Have reservoirs throughout pipe network to store treated water and provide gravity fed water. Develop, implement and update water safety plans. Fill local reservoirs prior to large storms to provide gravity flow. Hydrological monitoring stations. Rain gauging. Earth observation data. Enhanced inspection of infrastructure. the public of the risk of contamination during and after extreme rainfall events. water engineers of risks from water quality changes during extreme rainfall events, and how to manage the risk. Disseminate health advisory notices to the public with advice about dealing with the risks. Develop communication procedures to notify public when the water is safe. Issue boil water notices if appropriate. Possible mechanisms include posting leaflets, door-to-door visits, and radio and television announcements.

30 Increased erosion leading to more polluted run-off, with silt and nutrients. Increase in suspended sediment loads may exceed the treatment capacity of the water treatment facilities. Public health risk from contaminants entering the water distribution system. Land management Maintain vegetation in minimize erosion with buffer strips next to the public of the risk of planting schemes, buffer rivers. contamination during and strips and storm water after extreme rainfall management. events. Develop, implement and update water safety plans. Monitor water quality and adapt treatment processes to ensure that water quality is not compromised, such as by increasing sedimentation time and improving filtration systems. water engineers of risks from water quality changes during extreme rainfall events, and how to manage the risk. Disseminate health advisory notices to the public with advice about dealing with the risks. Develop communication procedures to notify public when the water is safe. Issue boil water notices if appropriate. Possible mechanisms include posting leaflets, door-to-door visits, and radio and TV announcements. Increased risk of landslides on steep slopes causing damage to infrastructure. Potential failure of the drinking-water supply system, and loss of service. Build treatment works and pipe networks away from slopes that are at risk of slippage. Reinforce slopes where there is a risk of slippage that may damage infrastructure. Hydrological monitoring stations. Rain gauging. Raise public awareness on risk of contamination during and after extreme rainfall events.

31 Public health risk from contaminants entering the water distribution system through damaged pipes. Reduced access to the affected areas. Develop, implement and update water safety plans. Implement leakage reduction plan, as leakage can contribute to landslides. Enhanced inspection of infrastructure. water engineers of risks from water quality changes during extreme rainfall events, and how to manage the risk. Disseminate health advisory notices to the public with advice about dealing with the risks. Develop communication procedures to notify the public when the water is safe. Issue boil water notices if appropriate. Possible mechanisms include posting leaflets, door-to-door visits, and radio and television announcements. Groundwater quality, particularly at shallow depths, may deteriorate. Increased lateral flow in soils may also spread contamination. Public health risk from contaminants entering the water distribution system. Develop, implement and update water safety plans. Consider constructing deeper wells. Ensure that wells are sealed to several metres below the water table. Monitor water quality and adapt treatment processes to ensure that water quality is not compromised. water resource managers and water engineers about the potential for lateral transport of pathogens and subsequent contamination of water.

32 Consider alternative Disseminate health sources. advisory notices to the public with advice about dealing with the risks. Develop communication procedures to notify the public when the water is safe. Issue boil water notices if appropriate. Community-managed piped water supplies See also key issue: Flooding increases See also utility-managed piped water supplies Increased risk of Potential failure of the landslides on steep drinking-water supply slopes causing damage system, and loss of to infrastructure. service. Public health risk from contaminants entering the water distribution system through damaged pipes. Where possible, avoid installing pipes on slopes that are at risk of slippage. Develop, implement and update water safety plans. Reinforce slopes where there is a risk of slippage that may damage infrastructure. Establish centralized support unit to provide technical and administrative assistance. the community about the damage that landslides can cause to infrastructure and the potential effect on the water supply system. Reduced access to the affected areas.

33 Public standpipes See also key issue: Flooding increases See also utility- and community-managed piped water supplies Increased risk of landslides on steep slopes causing damage to infrastructure. Loss of water supply to the standpipes. Site standpipes away from slopes that are at risk of slippage. Permanent loss of standpipe. Reinforce slopes where there is a risk of slippage that may damage infrastructure. If standpipes are located on at-risk slopes, ensure proper drainage. Local professional management (water kiosks) rather than free public standpipes will create positive incentives for management and protection of the infrastructure. the community about the damage that landslides can cause to infrastructure and the potential effect on the water supply system. Protected wells (boreholes and dug wells) See also key issue: Flooding increases Increased risk of Permanent loss of landslides on steep borehole or well as a slopes causing damage result of it being buried to infrastructure. under the landslide. Damage to the structure of the borehole or well, Build wells away from slopes that are at risk of slippage. Reinforce slopes where there is a risk of slippage that may damage infrastructure. Monitor microbial quality of water after the well or borehole has been renovated. the community about the damage that landslides can cause to wells and boreholes.