Water Retainer Research Articles

Improving outdoor human-thermal environment by optimizing the reflectance of water-retaining pavement through subjective field-based measurements

The role of urban surfaces in climate is recognized worldwide. Cool pavements such as reflective and water-retaining pavements contribute to the mitigation of urban heat. To optimize the cooling performance of a combination of reflective and evaporative characteristics, water-retaining (WR) pavements, with reflectance values of 13% (WR13) and 25% (WR25), were used and compared to a conventional asphalt pavement (AS). In addition to measuring surface and atmospheric temperatures, human-energy balance known as “human-thermal load” was assessed using perceptive responses obtained from participants (n = 78). Experimental insolation conditions were classified as low-, medium-, and high-based on radiation effects. Water-retaining pavements demonstrated significant surface temperature reductions compared to the overall AS; however, air temperature and humidity above the pavement were less sensitive, and they were not significantly different between the two distinct pavements. Under high insolation, local thermal comfort improved and skin temperatures of the lower body reduced. These consequently reduced the temperature perceived in the whole-body and improved the thermal environment on the surface of WR13. These results can be reasonably explained using the human-thermal load. The increase in thermal load from reflected solar radiation is limited below a certain level of insolation. The overall radiation received by WR13 was moderate from both ground-reflected and -sourced infrared radiation sources. The human-thermal load of WR13 was significantly different from that of AS under high insolation. A modest reflective pavement, such as WR13, is anticipated to improve human thermal comfort.

A new water-retaining paver block for reducing runoff and cooling pavement

In cities, urbanization tends to replace open soils that were naturally used for water storage with impermeable roofs and roads. These impervious surfaces have led to the development of urban heat island effects and to the occurrence of urban flooding during high intensity rainfalls. This phenomenon can be alleviated through the use of water-retaining (WR) pavements to hold rainwater for the subsequent evaporative cooling. These WR pavements are typically constructed as a porous pavement with water-holding media, which occupy the cavity of the matrix and decrease the amount of stored water for evaporation cooling. In this paper, a novel WR paver block is utilized to enhance the water storage capacity of the pavement system by retaining the water in the paver block without the need of water-holding layers. The new block retains the water in the block’s matrix by sealing the bottom and sides of the block with impervious media. The albedo, temperature, and WR capacities of this new paver block were measured and compared with conventional dense and pervious pavement options. It is found that even though the albedo of a new paver block is 0.10–0.15 lower than a conventional or pervious block, the new block can be 2–10 °C cooler. For 6 cm-thick paver blocks, the WR paver block can retain about 9.5 L/m2 water, which can be removed during a hot sunny day through evaporation. Pavements made of interlocking WR paver blocks can be used as a strategy to mitigate urban heat island and reduce urban runoff simultaneously.

Soil water-holding capacity mediates hydraulic and hormonal signals of near-isohydric and near-anisohydric Vitis cultivars in potted grapevines.

Grapevine (Vitis vinifera L.) expresses different responses to water stress, depending not only on genotype, but also on the influence of vineyard growing conditions or seasonality. Our aim was to analyse the effects on drought response of two grapevine cultivars growing on two soils, one water draining (WD) containing sand 80% volume and the other water retaining (WR), with no sand. Under these two different water-holding capacities Syrah, displaying a near-anisohydric response to water stress, and Cabernet Sauvignon (on the contrary, near-isohydric) were submitted to water stress in a pot trial. Xylem embolism contributed to plant adaptation to soil water deprivation: in both cultivars during late phases of water stress, however, in Syrah, already at moderate early stress levels. By contrast, Syrah showed a less effective stomatal control of drought than Cabernet Sauvignon. The abscisic acid (ABA) influenced tightly the stomatal conductance of Cabernet Sauvignon on both pot soils. In the near-anisohydric variety Syrah an ABA-related stomatal closure was induced in WR soil to maintain high levels of water potential, showing that a soil-related hormonal root-to-shoot signal causing stomatal closure superimposes on the putatively variety-induced anisohydric response to water stress.

Some characteristics of the seepage regime in the water-retaining dikes forming the high-level reservoir of a pumped-storage plant

In pumped-storage plants the water-re ta ining dikes forming the h ighl eve l reservoirs are subjected to quick changes in head. Thei r water l eve l may have a da i ly ampl i tude of 10-15 m and more, and its rate of rise or drop m a y reach 2-3 m / h . Under such conditions, in the body of the dike there is a pecul iar seepage regime whereby in the upstream shell seepage forces are produced which have a substantial effect on the sIope s tabi l i ty . These forces must be taken into account in the design of the dikes.*