How a climate-resilience splash pad doubles as an urban-cooling research site
A composite case study of a Phoenix-region splash pad designed as an integrated urban-cooling demonstration with bioswales, rain gardens, permeable paving, and a multi-year university research partnership.
Summary
A Phoenix-region city built a $2.7M splash pad designed explicitly as an integrated urban-cooling demonstration, combining the pad with bioswales, rain gardens, permeable paving, and a 5-year university research partnership measuring temperature, stormwater, and biodiversity outcomes. Year-one measurements showed a 6.4°F ambient cooling effect at the pad perimeter, 84% capture of design-storm runoff, and produced two peer-reviewed publications. The model is replicable for arid-climate cities pursuing dual recreation-and-resilience capital strategies.
Key metrics
Background: an arid-climate city under heat-and-water pressure
The Phoenix metropolitan region faces compounding climate-resilience pressures unique among major U.S. metros — extended summer extreme-heat events with ambient temperatures above 110°F now common across 30+ days per year, persistent multi-decade drought conditions affecting Colorado River allocation, and rapid population growth driving land-use intensification on increasingly heat-vulnerable urban surfaces. The city of Tempe, anchoring the metro's east side and home to the region's flagship public university, had been pursuing a multi-year urban-cooling and stormwater-management strategy through its sustainability office. By 2023, the strategy had produced individual capital projects in shade-tree planting, cool-pavement pilots, and stormwater bioswale demonstration sites, but lacked an integrated showcase project that combined recreation, cooling, and stormwater outcomes at flagship scale. The splash-pad project emerged from a strategic conversation between the parks department, sustainability office, and university urban-climate research center as a candidate flagship — recreation as the visible public benefit, cooling and stormwater as the underlying climate-resilience purpose, research partnership as the credibility anchor.
Funding model: a four-source resilience-recreation stack
The $2.7M capital stack reflected the project's hybrid character. Approximately $900,000 came from the city's parks capital fund, framed as a recreation investment within the existing parks-and-recreation capital plan. Approximately $850,000 came from an EPA Climate Pollution Reduction Grant focused on urban-cooling infrastructure, with the splash pad's green-infrastructure components (bioswales, rain gardens, permeable paving, native-shade tree canopy) qualifying as cooling infrastructure within the grant's eligibility framework. Approximately $600,000 came from an Arizona Water Infrastructure Finance Authority grant focused on stormwater-management demonstration projects, with the project's design-storm capture capability qualifying as eligible stormwater infrastructure. Approximately $350,000 came from the university's urban-climate research center, structured as a 5-year research-partnership funding contribution that includes both capital sensor-instrumentation and ongoing research operating support. The four-source stack required substantial inter-agency coordination but also unlocked categorical funding sources that no single funding mechanism could have provided alone.
Design choices: pad, bioswales, rain gardens, and permeable paving as one system
The design treats the splash pad and its surrounding 4.6-acre site as a single integrated system rather than a recreation feature with peripheral landscaping. The 3,800-square-foot pad sits at the system's hydrologic high point, with cascading water-management features descending across the site. Pad drain-down water and overflow flows through engineered bioswales lined with native riparian vegetation, into rain-garden depressions sized for the site's design-storm volume, through permeable-paving plaza surfaces, and into a final infiltration-and-recharge basin that returns capture volume to the regional aquifer. The pad itself uses recirculating water with a UV-and-chlorine treatment cycle, with periodic full drain-down water captured through the green-infrastructure system rather than discharged to municipal storm sewer. Native-shade tree canopy includes 84 mesquite, palo verde, and ironwood trees selected for low water demand and high cooling effectiveness, with irrigation supplied entirely from the site's captured stormwater rather than potable water.
Research partnership: instrumentation, methodology, and publication
The university partnership operates through a formal research-partnership agreement with the city signed at the project's groundbreaking. The site is instrumented with 24 fixed-position air-temperature sensors at heights of 1.5m and 4m, 12 surface-temperature radiometers, 8 soil-moisture sensors at depths from 0.1m to 1.0m, 4 weather stations (temperature, humidity, wind, solar radiation), 3 stormwater flow meters at the bioswale-to-rain-garden transitions, and a continuous-monitoring water-quality probe at the recharge basin. The research methodology compares the site against a paired-control comparison site (a similarly-sized non-resilience-designed park 1.2 miles away) using a difference-in-differences statistical framework. Year-one research outputs include two peer-reviewed publications (one in a urban-climate journal on the cooling effect, one in a stormwater-engineering journal on the runoff capture and infiltration performance), three conference presentations, and a publicly-accessible data dashboard that shows real-time site temperature, stormwater capture, and water-quality metrics.
Construction: integrated systems require integrated construction
Construction ran from August 2024 through April 2026 — a longer-than-typical timeline reflecting the integrated nature of the system. The general contractor specifically had both aquatic-construction and green-infrastructure-construction experience (only three regional firms qualified, and two ultimately bid). Site grading and earthwork ran August through November 2024 and was substantially more complex than typical pad construction because the site's hydrologic design required precise grading tolerances across the entire 4.6 acres, not just the pad footprint. Bioswale and rain-garden construction ran December 2024 through March 2025. Pad construction ran in parallel, with mechanical-building and recirculation systems completed by May 2025. Permeable-paving installation, native-tree planting, and sensor instrumentation ran summer-fall 2025. Commissioning ran through winter 2025, with formal opening over Earth Day weekend in April 2026 — deliberately timed to align with the city's annual sustainability-celebration programming.
First-year measurements: cooling, stormwater, and biodiversity
First-year research measurements produced three substantive findings. First, ambient cooling effect at the pad perimeter measured 6.4°F (3.6°C) below the paired-control site under summer extreme-heat conditions, with the cooling effect attributable roughly equally to the pad's evaporative effect, the native-tree canopy's transpiration effect, and the green-infrastructure surfaces' lower thermal mass relative to typical hardscape. Second, design-storm runoff capture measured 84% across the eight measurable storm events of the first water year, exceeding the project's 75% design target and providing roughly 1.4 acre-feet of aquifer recharge volume during the year. Third, the site's biodiversity index (measured through bird-survey, pollinator-survey, and reptile-survey work conducted by university graduate students) rose from a pre-construction baseline of 14 species to 47 species by year-end, with the native-vegetation bioswales and rain gardens supporting most of the increase. The findings were sufficiently strong that the city's sustainability office has begun planning two additional climate-resilience splash pads using the same design framework.
Operating realities: maintenance complexity is meaningful
The integrated-system design requires meaningfully more sophisticated maintenance than a typical splash pad. Bioswale and rain-garden vegetation requires seasonal management to maintain hydrologic function (sediment buildup at bioswale entries can reduce capture capacity by 30%+ if not managed), permeable paving requires periodic vacuum-cleaning to prevent surface clogging, and the native-tree canopy requires structural pruning during the establishment period to develop appropriate canopy form. The city's parks department has dedicated 0.5 FTE of specialized green-infrastructure maintenance labor to the site, in addition to typical pad-attendant staffing. Annual operating costs broke down as roughly $96,000 in standard pad operations (water, chemistry, electricity, labor), plus an additional $32,000 in research-related operating costs (sensor maintenance, data-collection labor, publication and presentation work) funded through the university partnership rather than the city operating budget.
Replicability: arid-climate cities and the resilience-recreation playbook
The Rio Salado model is replicable for arid-climate cities pursuing integrated climate-resilience capital strategies. Specific applicability is highest in southwestern U.S. metros (Phoenix, Tucson, Las Vegas, Albuquerque, El Paso, Fresno, San Diego inland), western Texas metros, and increasingly heat-vulnerable mountain-west metros. Critical preconditions include (1) a city sustainability office or comparable function with capacity to coordinate multi-source funding stacks, (2) a research-university partner with urban-climate or stormwater-engineering research depth and a willingness to commit 5+ year research partnership effort, and (3) site selection that can support a 4-6 acre integrated-system footprint rather than a small recreation-only footprint. The model is harder to execute for cities without sustainability-office capacity, without university research-partner access, or with site-selection constraints that don't support the larger footprint. The model is not particularly applicable to humid-temperate-climate cities where evaporative cooling effects are smaller and stormwater capture priorities differ — those cities should pursue different climate-resilience-recreation playbooks.
The strategic value of pairing recreation with research credibility
One of the project's most-replicated lessons is the strategic value of pairing visible public-recreation benefit with research-credible climate-resilience measurement. The pairing strengthens the project against two political-risk vectors that can independently weaken pure-recreation or pure-resilience capital projects. Pure-recreation projects can struggle to access climate and stormwater funding sources, and pure-resilience demonstration projects can struggle to maintain public political support during hot summer days when residents want a place to take their kids. The integrated project accesses both funding categories and maintains both public-political and research-credibility constituencies. The university partnership specifically functions not just as a research-credibility anchor but as a political-stability anchor — the existence of a 5-year research commitment makes the project meaningfully harder to defund or redirect under political turnover, since defunding would require winding down active university research with attendant academic-political cost.
Voices from the project
“We didn't build a splash pad with some plants around it. We built one integrated hydrologic and thermal system, and the splash pad happens to be the visible part. The bioswales and the trees are doing as much work as the pad.”
“Six and a half degrees of cooling at the pad perimeter is not a marketing number. It's a peer-reviewed measurement, and it's the difference between a heat-vulnerable neighborhood and a livable one on a 110-degree day.”
“The five-year research commitment makes this project politically uncrushable. You can't defund active university research without academic-political cost. That's a feature.”
Lessons learned
- Design pad and surrounding 4-6 acre site as one integrated hydrologic and thermal system, not pad-plus-landscaping.
- Stack city + EPA + state water + university research funding to assemble integrated-resilience capital budgets.
- Instrument the site for credible climate-resilience measurement — fixed-position sensors, paired-control methodology.
- Partner with a research university for both research credibility and political-stability anchoring.
- Use native arid-climate trees (mesquite, palo verde, ironwood) and irrigate from captured stormwater, not potable water.
- Budget for specialized green-infrastructure maintenance labor — bioswales and permeable paving are not low-maintenance.
- Time opening for sustainability-celebration calendar moments to maximize alignment with project narrative.
FAQ
How much cooling effect can a climate-resilience splash pad produce?
Peer-reviewed measurement at the Rio Salado composite recorded 6.4°F ambient cooling at the pad perimeter under summer extreme-heat conditions versus a paired-control site, attributable roughly equally to pad evaporation, native-tree transpiration, and green-infrastructure surface thermal effects. Effect sizes vary by climate zone — arid-climate sites show larger effects than humid-temperate sites.
Can EPA climate funding be used to build splash pads?
Splash pads themselves are generally not directly EPA-eligible, but their integrated green-infrastructure components — bioswales, rain gardens, permeable paving, native-tree canopy — typically qualify under EPA Climate Pollution Reduction and urban-cooling grant programs. The Rio Salado composite accessed roughly $850,000 in EPA funding through the green-infrastructure components specifically, not the pad itself.
What does a university research partnership add to a climate-resilience splash pad?
Three things: peer-reviewed measurement credibility for cooling and stormwater outcomes, ongoing publication and presentation visibility that strengthens the project's regional reputation, and political-stability anchoring through the academic-political cost of winding down active research. The Rio Salado partnership also funds approximately $32,000 in annual research-operating costs that the city would otherwise have to absorb.
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