Air Temperature Reductions at the Base of Tree Canopies.

Trees in urban settings have a significant role in regulating urban hydrologic cycles. Urban trees, either as standalone plantings or as part of a tree pit, are an increasingly popular stormwater management tool. Beyond their aesthetic contribution to urban environments, trees are widely accepted as reducing the ambient air temperature. However, there is limited long-term quantitative information regarding the temperature mitigation performed by urban trees through the use of temperature sensors over a large urban area. This study monitored air temperature at locations throughout the city of Camden, New Jersey. Sensors were installed under canopies of trees of different sizes throughout the city using a statistical experimental design. The tree size (small or large) and canopy (intersecting or nonintersecting), along with the street orientation (predominantly north-south or east-west) and time of day (daylight, nighttime, or full-day), were experimental design factors. Sensors attached to poles along the streets or in parking lots served as controls. This study recorded temperatures at 10-min intervals from early August through late November 2017 using logging thermistors mounted in radiation shields about 4 m above the ground surface. Using the maximum daily air temperature at control sites, all temperature data were categorized into three groups of hot, average, and cool days. The groups were analyzed separately using the analysis of variance to test the significance of the categorical variables. During hot days (a maximum temperature larger than 30°C), there was a meaningful statistical difference between recorded mean air temperatures under trees with intersecting canopies and the control sites. A categorical analysis of street orientation for hot and average days showed that during the daytime, east-west streets were hotter than north-south streets, while this trend reversed at night when north-south streets were hotter than east-west streets. For cool days, there were no differences for the studied categorical factors.

Long-term effects of three types of permeable pavements on nutrient infiltrate concentrations.

There is limited information about long-term effects of permeable pavement parking lots on concentrations of nutrients in infiltrates. A 0.40-ha parking lot that contained three types of permeable pavement including permeable interlocking concrete pavement (PICP), porous asphalt (PA) and pervious concrete (PC) was constructed in 2010 at a U.S. EPA facility in Edison, New Jersey. This study was conducted from October 2010 to August 2017. Water quality samples were collected from the rainfall, parking lot runoff, and infiltrate from these three pavement types. Samples were analyzed for parameters including NH3-N, NO2-N, NO3-N, TN, PO4-PO4, TOC, ORP and pH. Statistical methods were used to study infiltrate concentration changes with time. Results showed, for all analytes, there were no differences between permeable interlocking concrete pavement and pervious concrete median concentrations. Data showed distribution of species changed and supported nitrification processes. The trend varied with source. Nitrogen species showed slowly increasing trends in rainwater, PC and PICP infiltrate concentrations while phosphate concentration showed a slightly increasing trend in rainwater and porous asphalt infiltrate. It is recommended that communities select PC and PICP when nitrogen species are the pollutants of concern and PA is more suitable for orthophosphate removal.

Monitoring the performance of urban green infrastructure using a tensiometer approach.

Little is known about how stormwater exfiltrates from green infrastructure and few efforts have been undertaken to address this question. This study used tensiometers to monitor water exfiltration from an aggregate-filled storage gallery installed under permeable pavement. An 80-space parking lot was built at Seitz elementary school in Fort Riley, KS under an agreement between EPA and US Army during the summer of 2015. A network of twelve tensiometers and twelve monitoring wells was installed under and south of the storage gallery. Tensiometers were installed a various depths and distances to monitor soil moisture tension. The installation was used to monitor subsurface water flow patterns from the storage gallery under the permeable pavement site. The results of the study showed that soil moisture tension is larger at the shallower depths, decreasing with depth from the ground surface. Larger soil tension was associated with increased distance from the permeable pavement storage gallery. The results showed exfiltration from both the sidewalls and the bottom of the gallery while the changes in soil tension were larger for the tensiometer monitoring exfiltration from the side walls. Both the accumulated water depth inside the storage gallery and groundwater level rise were positively correlated with total rainfall depth. The calculated vertical flow rate was larger than the horizontal flow. The soil water tension change associated with storage gallery exfiltration was measured in a radius of <5 m from the storage gallery. Long-term peak groundwater level rise should be considered for design of the storage gallery depth to maintain the effective exfiltration. Understanding the exfiltration pathways aids with the placement and design the storage gallery. Additional research is necessary to understand how specific local parameters and vadose zone characteristics would affect the long-term exfiltration process.

Investigation clogging dynamic of permeable pavement systems using embedded sensors.

Permeable pavement is a stormwater control measure commonly selected in both new and retrofit applications. However, there is limited information about the clogging mechanism of these systems that effects the infiltration. A permeable pavement site located at the Seitz Elementary School, on Fort Riley, Kansas was selected for this study. An 80-space parking lot was built behind the school as part of an EPA collaboration with the U.S. Army. The parking lot design includes a permeable interlocking concrete pavement section along the downgradient edge. This study monitored the clogging progress of the pavement section using twelve water content reflectometers and three buried tipping bucket rain gauges. This clogging dynamic investigation was divided into three stages namely pre-clogged, transitional, and clogged. Recorded initial relative water content of all three stages were significantly and negatively correlated to antecedent dry weather periods with stronger correlations during clogged conditions. The peak relative water content correlation with peak rainfall 10-min intensity was significant for the water content reflectometers located on the western edge away from the eastern edge; this correlation was strongest during transition stage. Once clogged, rainfall measurements no longer correlated with the buried tipping bucket rain gauges. Both water content reflectometers and buried tipping bucket rain gauges showed the progress of surface clogging. For every 6 mm of rain, clogging advanced 1 mm across the surface. The results generally support the hypothesis that the clogging progresses from the upgradient to the downgradient edge. The magnitude of the contributing drainage area and rainfall characteristics are effective factors on rate and progression of clogging.

Introducing a water quality index for assessing water for irrigation purposes: A case study of the Ghezel Ozan River.

Rivers are one of the main water resources for agricultural, drinking, environmental and industrial use. Water quality indices can and have been used to identify threats to water quality along a stream and contribute to better water resources management. There are many water quality indices for the assessment and use of surface water for drinking purposes. However, there is no well-established index for the assessment and direct use of river water for irrigation purposes. The aim of this study was to adopt the framework of the National Sanitation Foundation Water Quality Index (NSFWQI) and, with adjustments, apply it in a way which will conform to irrigation water quality requirements. To accomplish this, the NSFWQI parameters for drinking water use were amended to include water quality parameters suitable for irrigation. For each selected parameter, an individual weighting chart was generated according to the FAO 29 guideline. The NSFWQI formula was then used to calculate a final index value, and for each parameter an acceptable range in this value was determined. The new index was then applied to the Ghezel Ozan River in Iran as a case study. A forty five year record of water quality data (1966 to 2010) was collected from four hydrometery stations along the river. Water quality parameters including Na+, Cl-, pH, HCO-3, EC, SAR and TDS were employed for water quality analysis using the adjusted NSFWQI formula. The results of this case study showed variation in water quality from the upstream to downstream ends of the river. Consistent monitoring of the river water quality and the establishment of a long term management plan were recommended for the protection of this valuable water resource.