Editing IPCC:AR6/WGII/Chapter-14 (section)

=== 14.5.3 Water Resources ===

<div id="h2-10-siblings" class="h2-siblings"></div>

Climate change poses increasing threats to North American aquatic ecology, water quality, water availability for human uses, and flood exposure, through reductions in snow and ice, increases in extreme precipitation and hotter droughts. Adaptation will be impeded in cases where there are conflicts over competing interests or unintended consequences of uncoordinated efforts, heightening the importance of cooperative, scenario-based water resource planning and governance ( ''high confidence'' ).

<div id="14.5.3.1" class="h3-container"></div>

<span id="observed-impacts"></span>
==== 14.5.3.1 Observed Impacts ====

<div id="h3-6-siblings" class="h3-siblings"></div>

North American water resources continue to be affected by ongoing warming, with impacts driven by reductions in snow and ice, increases in extreme precipitation and hotter droughts ( ''high confidence'' ) ( [[#14.2|Section 14.2]] ; [[#Fleming--2014|Fleming and Dahlke, 2014]] ; [[#Mortsch--2015|Mortsch et al., 2015]] ; [[#Dudley--2017|Dudley et al., 2017]] ; [[#Fyfe--2017|Fyfe et al., 2017]] ; [[#McCabe--2017|McCabe et al., 2017]] ; [[#Chavarria--2018|Chavarria and Gutzler, 2018]] ; [[#Lall--2018|Lall et al., 2018]] ; [[#Bonsal--2019|Bonsal et al., 2019]] ; [[#USGCRP--2019|USGCRP, 2019]] ). The cascading effects of severe droughts, floods, sediment mobilisation, HABs and pathogen contamination episodes have revealed the vulnerability and exposure of large numbers of people and economic activities to those hazards.

North America’s dams, levees, wastewater-management and water conveyance facilities have improved water supply safety and have reduced flood and drought risks, but a substantial portion of that infrastructure is ageing and inadequate for modern conditions ( [[#Ho--2017|Ho et al., 2017]] ; [[#Tellman--2018|Tellman et al., 2018]] ; [[#Carlisle--2019|Carlisle et al., 2019]] ; [[#FEMA--2019|FEMA, 2019]] ; [[#ASCE--2021|ASCE, 2021]] ). Increasingly heavy precipitation from a variety of storm types has affected parts of North America ( [[#Feng--2016|Feng et al., 2016]] ; [[#Prein--2017a|Prein et al., 2017a]] ; [[#Kunkel--2019|Kunkel and Champion, 2019]] ; [[#Kunkel--2020|Kunkel et al., 2020]] ), contributing to contamination from combined sewer overflows ( [[#Olds--2018|Olds et al., 2018]] ) and increased flood damages that are partially attributed to anthropogenic climate change ( [[#van%20der%20Wiel--2017|van der Wiel et al., 2017]] ; Davenport, 2021). Extreme precipitation events have overwhelmed water control infrastructure, imperilling public safety and contributing to extensive damages in parts of North America ( [[#Kytomaa--2019|Kytomaa et al., 2019]] ; [[#Vano--2019|Vano et al., 2019]] ; [[#White--2019|White et al., 2019]] ). Damages stem from extremity of the event and prior land-use and infrastructure decisions ( ''high confidence'' ) ''.''

In South Carolina, 5 days of heavy rainfall in October 2015 caused the failure of more than 50 dams and some levees, significantly magnifying destruction from the floodwaters ( [[#FEMA--2016|FEMA, 2016]] ). Slow-moving, destructive storms like hurricanes Harvey (2017) and Florence (2018) have caused significant flooding ( [[#van%20Oldenborgh--2017|van Oldenborgh et al., 2017]] ; [[#Paul--2019b|Paul et al., 2019b]] ). In those cases, urban sprawl may have altered storm dynamics ( [[#Zhang--2018b|Zhang et al., 2018b]] ), while increased asset exposure to the flood hazard amplified the multi-billion-dollar losses ( [[#Klotzbach--2018|Klotzbach et al., 2018]] ; [[#Trenberth--2018|Trenberth et al., 2018]] ). A substantial fraction of the damage from hurricane Harvey’s extreme rainfall has been attributed to anthropogenic climate change (see Box 14.5; [[#Emanuel--2017|Emanuel, 2017]] ; [[#Risser--2017|Risser and Wehner, 2017]] ). A near disaster at California’s Oroville dam in 2017 was caused by inadequate infrastructure design and maintenance together with an unusually large number of atmospheric river (AR) storms. The event required emergency reservoir spills while the state was beginning recovery from the extreme 2012–2016 drought ( [[#Vano--2019|Vano et al., 2019]] ; [[#White--2019|White et al., 2019]] ).

In Mexico, some poor neighbourhoods and informal settlements are located in areas exposed to recurrent flooding. Residents often lack access to public services and technical resources for risk reduction, which heightens their vulnerability ( [[#Castro--2019|Castro and De Robles, 2019]] ).

Population growth and urban development have increased the exposure and vulnerability of Canadian communities to flood damages, with cumulative damages (including uninsured losses) exceeding 10 billion USD in the past decade ( [[#The%20Geneva%20Association--2020|The Geneva Association et al., 2020]] ). Recurring floods are particularly costly (e.g., New Brunswick) ( [[#Beltaos--2015|Beltaos and Burrell, 2015]] ; [[#Kovachis--2017|Kovachis et al., 2017]] ). Floods in High River, AB (2013) and Gatineau, QC (2017, 2019) initiated considerations of building flood resilience including planned retreat ( [[#Saunders-Hastings--2020|Saunders-Hastings et al., 2020]] ).

Extended and severe droughts in the western USA, northern Mexico and Canadian Prairies, exacerbated by higher temperatures, have caused economic and environmental damage ( [[#Williams--2013|Williams et al., 2013]] ; Agha Kouchak et al., 2015; [[#Diaz--2016|Diaz et al., 2016]] ; [[#Bain--2018|Bain and Acker, 2018]] ; [[#Lopez-Perez--2018|Lopez-Perez et al., 2018]] ; [[#Ortega-Gaucin--2018|Ortega-Gaucin et al., 2018]] ; [[#Xiao--2018|Xiao et al., 2018]] ; [[#Martinez-Austria--2019|Martinez-Austria et al., 2019]] ; [[#Bonsal--2020|Bonsal et al., 2020]] ; [[#Martin--2020b|Martin et al., 2020b]] ; [[#Milly--2020|Milly and Dunne, 2020]] ; [[#Overpeck--2020|Overpeck and Udall, 2020]] ). Droughts have intensified tensions among competing water-use interests and accelerated depletion of groundwater resources ( ''high confidence'' ) ( [[#14.5.4|Section 14.5.4]] ; [[#Pauloo--2020|Pauloo et al., 2020]] ).

Climate trends are affecting riverine, lake and reservoir water quality ( ''medium confidence'' ). Droughts and increased evapotranspiration have impaired water quality by concentrating pollutants in diminished water volumes ( [[#Paul--2019a|Paul et al., 2019a]] ). Cyanobacterial blooms and pathogen exposure events are increasing in frequency, intensity and duration in North America ( [[#Taranu--2015|Taranu et al., 2015]] ). They are closely associated with observed changes in precipitation intensity and associated nutrient loading (e.g., agricultural runoff, sanitary sewer overflows), elevated water temperatures and eutrophication ( [[#Michalak--2013|Michalak et al., 2013]] ; [[#Michalak--2016|Michalak, 2016]] ; [[#Trtanj--2016|Trtanj et al., 2016]] ; [[#Chapra--2017|Chapra et al., 2017]] ; [[#IBWC--2017|IBWC, 2017]] ; [[#Williamson--2017|Williamson et al., 2017]] ; [[#Olds--2018|Olds et al., 2018]] ; [[#Coffey--2019|Coffey et al., 2019]] ). These events endanger human and animal health, recreational and drinking water uses and aquatic ecosystem functioning, and cause economic losses ( [[#Michalak--2013|Michalak et al., 2013]] ; [[#Bullerjahn--2016|Bullerjahn et al., 2016]] ; [[#Chapra--2017|Chapra et al., 2017]] ; [[#Huisman--2018|Huisman et al., 2018]] ). Households and communities dependent on substandard wells, unimproved water sources or deficient water provision systems are more exposed than others to experience climate-related impairment of drinking water quality ( [[#14.5.6.5|Section 14.5.6.5]] ; [[#Allaire--2018|Allaire et al., 2018]] ; [[#Baeza--2018|Baeza et al., 2018]] ; [[#California%20State%20Water%20Resources%20Control%20Board--2021|California State Water Resources Control Board, 2021]] ; [[#Navarro-Espinoza--2021|Navarro-Espinoza et al., 2021]] ; Water and Tribes Initiative, 2021).

<div id="14.5.3.2" class="h3-container"></div>

<span id="projected-impacts-and-risks"></span>
==== 14.5.3.2 Projected Impacts and Risks ====

<div id="h3-7-siblings" class="h3-siblings"></div>

Climate change is projected to amplify current trends in water resource impacts, potentially reducing water supply security, impairing water quality and increasing flood hazards to varying degrees across North America ( ''high confidence'' ). Examples are presented in Table 14.3.

'''Table 14.3 |''' Selected projected water resource impacts in North America

{| class="wikitable"
|-
! Climate drivers and processes

! Examples of future risks and impacts

! Location (see Figure 14.1)

! References

|-
| Warming-induced reductions in mountain snow and glacial mass

| Projected decreases in annual and late-summer streamflow from high-elevation reaches of snow-fed rivers, affecting stream ecology and water supplies ( ''high confidence'' )

| US-NW, US-SW, CA-BC, CA-PR

| [[#Jost--2012|Jost et al. (2012)]] ; [[#Solander--2018|Solander et al. (2018)]] ; [[#Bonsal--2019|Bonsal et al. (2019)]] ; Milly and Dunne (2020)

|-
| Earlier seasonal snowmelt runoff

| Greater winter/early spring flooding risks and reduced summer surface water availability, intensifying seasonal mismatch with water demands ( ''high confidence'' );

increased challenges for balancing multi-purpose reservoir objectives (e.g., flood management, water supply, ecological protection and hydropower) ( ''high confidence'' )

| US-NW, US-SW, CA-BC, CA-PR

| Cohen et al. (2015); Dettinger et al. (2015); [[#Bonsal--2019|Bonsal et al. (2019)]] ; [[#Bonsal--2020|Bonsal et al. (2020)]] ; [[#RMJOC--2020|RMJOC (2020)]] ; [[#Bureau%20of%20Reclamation--2021d|Bureau of Reclamation (2021d)]]

|-
| Earlier seasonal snowmelt runoff

| Possible reductions in water supply security ( ''medium confidence'' ); reduced viability of some small-scale irrigation systems ( ''medium confidence'' )

| US-SW

| [[#Medellin-Azuara--2015|Medellin-Azuara et al. (2015)]] ; [[#Ullrich--2018|Ullrich et al. (2018)]] ; [[#Bai--2019|Bai et al. (2019)]] ; Milly and Dunne (2020); [[#Ray--2020|Ray et al. (2020)]] ; [[#Bureau%20of%20Reclamation--2021b|Bureau of Reclamation (2021b)]] ; [[#Bureau%20of%20Reclamation--2021a|Bureau of Reclamation (2021a)]] ; [[#Bureau%20of%20Reclamation--2021c|Bureau of Reclamation (2021c)]]

|-
| Changes in seasonal timing and/or total annual runoff

| Impacts on electric power generation ( ''medium confidence'' ) varying by location and type of generation

| US-SW, US-NW, CA-QC

| [[#Haguma--2014|Haguma et al. (2014)]] ; [[#Bartos--2015|Bartos and Chester (2015)]] ; Guay et al. (2015); [[#Turner--2019b|Turner et al. (2019b)]] ; [[#RMJOC--2020|RMJOC (2020)]] ; [[#Bureau%20of%20Reclamation--2021d|Bureau of Reclamation (2021d)]]

|-
| Changes in seasonal timing and/or total annual runoff

| Impacts on urban water supplies

| CA-QC

| [[#Foulon--2019|Foulon and Rousseau (2019)]]

|-
| Warming-related increased imbalance between renewable surface water supplies and consumptive water demands

| Greater pressures on groundwater resources, possible increased aquifer depletion, reduced baseflow into surface streams and reduced long-term water supply sustainability ( ''medium confidence'' )

| US-SW, US-SP, US-SE, MX-N, MX-NW

| [[#Bauer--2015|Bauer et al. (2015)]] ; [[#Molina-Navarro--2016|Molina-Navarro et al. (2016)]] ; [[#Russo--2017|Russo and Lall (2017)]] ; Brown et al. (2019b); [[#Nielsen-Gammon--2020|Nielsen-Gammon et al. (2020)]] ; [[#Bureau%20of%20Reclamation--2021b|Bureau of Reclamation (2021b)]]

|-
| Warming-related drought amplification

| Reduced water availability for human uses and ecological functioning ( ''medium'' to ''high confidence'' ) varying by location; increased evaporative losses from reservoirs

| Widespread especially:

US-SW, US-NP, US-SP, CA-PR, MX-NW, MX-N

| [[#Prein--2016|Prein et al. (2016)]] ; [[#Dibike--2017|Dibike et al. (2017)]] ; [[#Lall--2018|Lall et al. (2018)]] ; [[#Paredes-Tavares--2018|Paredes-Tavares et al. (2018)]] ; Martinez-Austria et al. (2019); [[#Tam--2019|Tam et al. (2019)]] ; [[#Martin--2020b|Martin et al. (2020b)]] ; Milly and Dunne (2020); [[#Overpeck--2020|Overpeck and Udall (2020)]] ; [[#Williams--2020|Williams et al. (2020)]] ; [[#Bureau%20of%20Reclamation--2021b|Bureau of Reclamation (2021b)]]

|-
| Heavier and/or prolonged rainfall events

| Flooding, infrastructure and property damage ( ''medium'' to ''high confidence'' ) varying by location; increased erosion and debris flows with impacts on public safety, reservoir sedimentation and stream ecology (hazards amplified in watersheds affected by wildfires)

| Widespread especially:

US-SE, US-NE, US-NP, US-SP, US-SW, CA-BC, MX-CE, MX-NE, MX-SE

| [[#Feng--2016|Feng et al. (2016)]] ; [[#Emanuel--2017|Emanuel (2017)]] ; [[#Prein--2017a|Prein et al. (2017a)]] ; [[#Prein--2017b|Prein et al. (2017b)]] ; [[#Haer--2018|Haer et al. (2018)]] ; [[#Kossin--2018|Kossin (2018)]] ; Mahoney et al. (2018); [[#Thistlethwaite--2018|Thistlethwaite et al. (2018)]] ; [[#Curry--2019|Curry et al. (2019)]] ; [[#Larrauri--2019|Larrauri and Lall (2019)]] ; [[#Wobus--2019|Wobus et al. (2019)]] ; Ball et al. (2021)

|-
| Heavier and/or prolonged rainfall events

| Water quality impairment, increasing HAB events due to increased sediment and nutrient loading together with warming; greatest impacts in humid areas with extensive agriculture ( ''medium to high confidence'' ) varying by location

| US-MW, US-NE, US-SE, US-NP, US-SP, CA-ON, CA-AT, MX-NE, MX-NW

| [[#Alam--2017|Alam et al. (2017)]] ; [[#Chapra--2017|Chapra et al. (2017)]] ; Sinha et al. (2017); Ballard et al. (2019)

|-
| Increasingly variable precipitation

| Highly variable precipitation poses challenges for water management, worsening water supply and flooding risks; atmospheric river events are projected to increase variability by dominating future North American west coast precipitation ( ''medium confidence'' )

| US-SW, US-NW, CA-BC

| [[#Gershunov--2019|Gershunov et al. (2019)]] ; Huang et al. (2020)

|-
| Hotter summer season

| Evaporative losses from reservoirs are projected to increase significantly ( ''very high confidence'' )

| US-SW, US-NW, US-NP

| [[#Bureau%20of%20Reclamation--2021b|Bureau of Reclamation (2021b)]]

|}

Projected long-term reduction in water availability in the southwest US and northern Mexico (e.g., from the Colorado and Rio Grande rivers) will have substantial ecological and economic impacts given the region’s heavy water demands ( ''high confidence'' ) ( [[#Lall--2018|Lall et al., 2018]] ; [[#Paredes-Tavares--2018|Paredes-Tavares et al., 2018]] ; [[#Martinez-Austria--2019|Martinez-Austria et al., 2019]] ; [[#Milly--2020|Milly and Dunne, 2020]] ; [[#Williams--2020|Williams et al., 2020]] ). Increased water scarcity will intensify the need to address competing interests across state and national boundaries, including honouring commitments to Indigenous Peoples who have long struggled with inadequate access to their water entitlements and marginalisation in water resource planning ( [[#Mumme--1999|Mumme, 1999]] ; [[#Cozzetto--2013b|Cozzetto et al., 2013b]] ; [[#Mumme--2016|Mumme, 2016]] ; [[#McNeeley--2017|McNeeley, 2017]] ; [[#Radonic--2017|Radonic, 2017]] ; [[#Robison--2018|Robison et al., 2018]] ; [[#Curley--2019|Curley, 2019]] ; Water and Tribes Initiative, 2020; [[#Wilder--2020|Wilder et al., 2020]] ).

Increased scarcity of renewable water relative to legally allocated or desired uses may develop in many parts of North America. A detailed analysis of projected water demands (consumptive uses) and availability found increasingly frequent shortages in several watersheds across the USA ( [[#Brown--2019b|Brown et al., 2019b]] ). This might lead to maladaptive increased groundwater mining, or alternatively to policies promoting sustainable balancing of water consumption with renewable supplies, for example, by facilitating voluntary water transfers or improving enforcement of groundwater rights ( [[#Colorado%20River%20Basin%20Stakeholders--2015|Colorado River Basin Stakeholders, 2015]] ; California Natural Resources Agency et al., 2020; [[#Colorado%20Water%20Conservation%20Board--2020|Colorado Water Conservation Board, 2020]] ; [[#Pauloo--2020|Pauloo et al., 2020]] ).

Climate change is projected to reduce groundwater recharge in major southwest US aquifers (e.g., Southern High Plains, San Pedro and Wasatch Front), exacerbating their ongoing depletion due to unsustainable pumping. Other aquifers, especially those farther north, face uncertain or possibly increasing recharge ( ''medium confidence'' ) ( [[#Meixner--2016|Meixner et al., 2016]] ).

Projected changes in temperature and precipitation present direct risks to North American water quality, varying with regional and watershed contexts ( [[#Chapra--2017|Chapra et al., 2017]] ; [[#Coffey--2019|Coffey et al., 2019]] ; [[#Paul--2019a|Paul et al., 2019a]] ), and related to streamflow, population growth ( [[#Duran-Encalada--2017|Duran-Encalada et al., 2017]] ) and land-use practices ( ''medium confidence'' ) ( [[#Mehdi--2015|Mehdi et al., 2015]] ). Harmful algal blooms increase in frequency across the USA ( [[#Wells--2015|Wells et al., 2015]] ) with the highest risk projected for the Great Plains and Northeast USA, and greatest economic impacts from lost recreation value in the southeast USA ( [[#Chapra--2017|Chapra et al., 2017]] ).

The diversity of climate regimes across North America results in regional differences in water-related climate-change risks (Figure 14.4).

<div id="14.5.3.3" class="h3-container"></div>

<span id="adaptation"></span>
==== 14.5.3.3 Adaptation ====

<div id="h3-8-siblings" class="h3-siblings"></div>

North American water planners and policy makers have abandoned stationarity assumptions ( [[#Milly--2015|Milly et al., 2015]] ) to address climate change. Transboundary institutions, government agencies and professional organisations are taking the lead on adaptation planning and implementation (ASCE, 2018b; [[#Clamen--2018|Clamen and Macfarlane, 2018]] ; International Joint Commission, 2018). Major water agencies are using climate scenarios to identify vulnerabilities and evaluate adaptation options ( [[#Yates--2015|Yates et al., 2015]] ; [[#Vogel--2016|Vogel et al., 2016]] ; [[#California%20Department%20of%20Water%20Resources--2019|California Department of Water Resources, 2019]] ; [[#Ray--2020|Ray et al., 2020]] ; [[#Bureau%20of%20Reclamation--2021d|Bureau of Reclamation, 2021d]] ).

The Water Utility Climate Alliance advises municipal water providers to address uncertainty by considering a wide range of plausible future climate conditions ( [[#WUCA--2010|WUCA, 2010]] ). In some areas, the impacts of wildfires on water supply resiliency are being considered ( [[#Martin--2016|Martin, 2016]] ). Many North American Indigenous Peoples are engaged in climate-change adaptation planning, although these efforts may be hampered by the complicated legal and administrative setting in which they must operate ( [[#Norton-Smith--2016a|Norton-]] [[#Smith--2016a|Smith et al., 2016a]] ; [[#McNeeley--2017|McNeeley, 2017]] ).

Recent climate extremes have heightened governmental attention to climate-change impacts (e.g., California Natural Resources Agency et al., 2020). Droughts have exposed shortcomings in water management and governance ( [[#Gray--2015|Gray et al., 2015]] ; [[#Xiao--2017b|Xiao et al., 2017b]] ; [[#Lopez-Perez--2018|Lopez-Perez et al., 2018]] ) spurring legislation and administrative changes to improve groundwater regulation and documentation of water rights ( [[#California%20Department%20of%20Food%20and%20Agriculture--2017|California Department of Food and Agriculture, 2017]] ; [[#Miller--2017|Miller, 2017]] ; [[#Lund--2018|Lund et al., 2018]] ; [[#Hanak--2019|Hanak et al., 2019]] ). Water allocation policies are being reassessed to enhance equity, sustainability and flexibility through shortage sharing agreements, improved groundwater regulation and voluntary water transfers. Developments include an interstate drought management agreement for the Colorado River ( [[#US%20Law--2019|US Law, 2019]] ), and agreements between the USA and Mexico to provide pulse flows to benefit the ecology of the Colorado River Delta ( [[#Pitt--2017|Pitt and Kendy, 2017]] ). Statewide water planning in Colorado has emphasised building drought resilience (e.g., by facilitating temporary water transfers) ( [[#Colorado%20State%20Government--2015|Colorado State Government, 2015]] ; [[#Yates--2015|Yates et al., 2015]] ). At local scales, there have been innovations in cooperative watershed protection and water resource planning ( [[#Cantú--2016|Cantú, 2016]] ). Indigenous Peoples are playing an increasing role in identifying equitable and resilient options for adaptation by contributing their knowledge and voicing their perspectives on the importance of healthy water bodies for human and environmental well-being ( [[#Norton-Smith--2016a|Norton-]] [[#Smith--2016a|Smith et al., 2016a]] ; Water and Tribes Initiative, 2020). Collaboration between stakeholders, policymakers and scientists is increasingly common in water resources adaptation planning and assessment.

Examples of adaptation include increasing adoption of water-saving irrigation methods in California ( [[#Cooley--2016|Cooley, 2016]] ), experimentation with using flood waters to enhance groundwater recharge ( [[#Kocis--2017|Kocis and Dahlke, 2017]] ; [[#California%20Department%20of%20Water%20Resources--2018|California Department of Water Resources, 2018]] ) and agricultural land management programmes, including developing riparian buffers to protect water quality ( [[#14.5.4|Section 14.5.4]] ; [[#Mehdi--2015|Mehdi et al., 2015]] ; [[#Schoeneberger--2017|Schoeneberger et al., 2017]] ). Indigenous Peoples are building upon traditional practices to adapt to the effects of climate change, for example, by working jointly to recharge local aquifers ( [[#Basel--2020|Basel et al., 2020]] ).

Water-right laws, interstate compacts and international treaties regarding transboundary water shape the context for climate-change adaptation, but the possibility of long-term climate change typically was not contemplated at their inception. Gaps in coverage and vaguely defined terms can lead to tensions and disputes, especially in areas facing increased aridity, creating difficulties for adaptation. For example, unregulated pumping of groundwater for irrigation during short-term droughts can serve as an adaptation to acute conditions ( [[#14.5.4|Section 14.5.4]] ), but if persisting in the long term, it can deplete finite groundwater resources and de-water hydrologically connected rivers. Such outcomes have engendered bitter and costly interstate conflicts in the USA, some even reaching the US Supreme Court including ''Texas v. New Mexico'' (Rio Grande) and ''Florida v. Georgia'' (Apalachicola-Chattahoochee-Flint).

Transboundary rivers that exemplify the need to address climate impacts include the Colorado ( [[#Gerlak--2013|Gerlak et al., 2013]] ), Columbia ( [[#Cosens--2016|Cosens et al., 2016]] ) and Rio Grande/Rio Bravo ( [[#Mumme--1999|Mumme, 1999]] ; [[#Mumme--2016|Mumme, 2016]] ; [[#Garrick--2018|Garrick et al., 2018]] ; [[#Payne--2020|Payne, 2020]] ). Drought emergencies can open opportunities for progress on collaborative adaptive governance, but such windows may quickly close when wetter conditions return (Sullivan, (2019).

Water serves a wide variety of environmental functions and human uses as it moves through North America’s river basins, so the impacts of climate change are expected to be widespread and multifaceted. This increases the importance of collaborative adaptation efforts that are equitable, transparent and give voice to differing values, perspectives and entitlements across a broad socioeconomic spectrum of urban and rural, Indigenous and non-Indigenous participants ( [[#Miller--2016|Miller et al., 2016]] ; [[#Cosens--2018|Cosens et al., 2018]] ). Adaptation planning may be hampered by conflicting interests, jurisdictional boundaries and inherent interconnections between actions and impacts at different points throughout a watershed or river basin. Differential power relationships, decision-making authority and access to information also can interfere with effective adaptive governance, while equitable processes for decision making bolstered by reliable shared information can help to overcome those impediments ( [[#Cosens--2016|Cosens et al., 2016]] ; [[#Arnold--2017|Arnold et al., 2017]] ; [[#Cosens--2018|Cosens et al., 2018]] ; [[#Porter--2018|Porter and Birdi, 2018]] ).

Across North America, there are growing signs of progress towards adaptive water governance and implementation of climate-resilient, and ecosystem-based, water management solutions ( [[#Colorado%20River%20Basin%20Stakeholders--2015|Colorado River Basin Stakeholders, 2015]] ). California’s approach to groundwater sustainability regulation intends to foster such collaborative problem-solving by giving local Groundwater Sustainability Agencies the authority to design locally appropriate plans to meet state-defined sustainability goals ( [[#State%20of%20California--2014|State of California, 2014]] ; [[#Miller--2017|Miller, 2017]] ). As evidenced by the US interstate disputes, the greatest difficulties arise in cases where stark upstream–downstream differences in interests leave little room for mutual benefit. Severe aridification may test the limits of adaptive capacity.

Research on water diplomacy recommends broadening negotiations beyond a narrow focus on zero-sum issues, like rigid water allocations, to embrace a more diverse set of shared interests including the need for flexibility to respond to changing conditions. A process for ongoing inclusive engagement of a watershed’s stakeholders in mutual social, policy and science learning is important. Such mutual learning can build trust and establish a common platform of credible information for co-creation of adaptation solutions. In addition, better understanding of the policy positions and constraints of others can help stakeholders to identify workable solutions to contentious water management issues ( [[#Payne--2020|Payne, 2020]] ; [[#Wilder--2020|Wilder et al., 2020]] ). Cooperation between Mexico and the USA on mapping and assessment of transboundary aquifers is a product of such ongoing engagement ( [[#Callegary--2018|Callegary et al., 2018]] ; [[#Sanchez--2018|Sanchez et al., 2018]] ). Other examples of the benefits of sustained engagement are provided by a set of co-management arrangements between state, federal and Indigenous authorities on water management for fishery restoration in the US Pacific Northwest ( [[#Tsatsaros--2018|Tsatsaros et al., 2018]] ) and Indigenous involvement in multi-level co-management of water resources in Canada’s Northwest Territories ( [[#Latta--2018|Latta, 2018]] ).

<div id="14.5.4" class="h2-container"></div>

<span id="food-fibre-and-other-ecosystem-products"></span>