Variability of drainage and solute leaching in heterogeneous urban vegetation environs

Abstract

Abstract. Deep percolation enhancement from recycled wastewater irrigation may contribute to salt accumulation and water table elevation that can ultimately cause soil and ground water degradation. Variation of drainage rate and solute leaching were investigated in an urban park containing heterogeneous landscape plants that were irrigated with recycled wastewater. Field monitoring was undertaken at Veale Gardens in the Adelaide Parklands, Australia. Based on landscape variation in Veale Gardens, two landscape zones were defined: one being largely covered with turf grasses with few trees and shrubs (MG) with the second zone being mostly trees and shrubs with intermittent turf grasses (MT). Experiments were performed on two zero-tension lysimeters placed horizontally 100 cm below ground to monitor the variation of volume and quality indicators of drained water for four seasons. The outcomes showed a significant variation of drainage quantity and quality in the MT and MG zones. The low vegetation cover in the MG zone resulted in more drained water than in the high vegetation cover (MT zone). In both zones, more drainage water was collected in winter than in other seasons. This is in spite of the input water showing a maximum rate in summer. The seasonal salinities measured in the two lysimeters showed very similar trends with the lowest salinity rate in autumn with the levels increasing through winter and spring. Chemical analyses of leachate solute and salt loading indicated no impact from using recycled wastewater.

Comparing Three Approaches of Evapotranspiration Estimation in Mixed Urban Vegetation: Field-Based, Remote Sensing-Based and Observational-Based Methods

“…The SWB shows that water management at Veale Gardens efficiently maintains the plants without over-irrigating the landscaping [13,20]. The observed leaching fraction of 0.16 is a reasonable value to keep soil salinity within the range tolerated by the mixed plantings [45].…”

“…In the case of non-agricultural systems, such as inner-city gardens and urban parks, the heterogeneous nature of vegetation and landscapes, together with the high spatial and temporal variability of soil and water characteristics, and the variability of management and watering practices [10] contribute to greatly increased complexity in the ET estimation of urban vegetation [11,12]. This is of even more concern when wastewater irrigation is occurring due to the risk of nutrient leaching that, in the long term, can result in soil and groundwater contamination [10,13].…”

“…The Adelaide Parklands includes a total of 29 parks that form a green belt of approximately 7.6 km 2 encircling the city centre of Adelaide. VG is fully covered by kikuyu turf grasses and also contains more than 60 species of trees and shrubs that are irrigated using recycled wastewater (EC < 2 dS/m) [13]. Thirty years of meteorological records for Adelaide collected at the Kent Town station located 2.9 km from the study site show that Adelaide experiences mostly warm summers (December-February) and fairly cold winters (June-August).…”

“…The lysimeter in landscape zone 2 was buried close to a tree with effective root zone of one meter. The installation method for the pan lysimeters is described in detail by Nouri et al [13].…”

Habitat complexity influences fine scale hydrological processes and the incidence of stormwater runoff in managed urban ecosystems

“…As extreme precipitation events are likely to increase with climate change (Yilmaz et al, 2014), the effective management of hydrological processes and related ecosystem services such as stormwater drainage, runoff mitigation, soil water storage and purification is becoming increasingly important to create more sustainable and resilient cities and towns (Bolund and Hunhammar, 1999;Cunningham et al, 2010;Pauleit and Duhme, 2000;Nouri et al, 2013).…”