Rainwater Reservoir Research Articles

빗물 재활용을 위한 모래 정화층의 폐색특성을 고려한 비점오염원 제거 예측 모델 연구

An artificial rainwater reservoir installed in urban areas for recycling rainwater is an eco-friendly facility for reducing storm water effluence. However, in order to recycle the rainwater directly, the artificial rainwater reservoir requires an auxiliary system that can remove non-point source pollutants included in the initial rainfall of urban area. Therefore, the conventional soil filtration technology is adopted to capture non-point source pollutants in an economical and efficient way in the purification system of artificial rainwater reservoirs. In order to satisfy such a demand, clogging characteristics of the sand filter layers with different grain-size distributions were studied with real non-point source pollutants. For this, a series of lab-scale chamber tests were conducted to make a prediction model for removal of non-point source pollutants, based on the clogging theory. The laboratory chamber experiments were carried out by permeating two types of artificially contaminated water through five different types of sand filter layers with different grain-size distributions. The two artificial contaminated waters were made by fine marine-clay particles and real non-point source pollutants collected from motorcar roads of Seoul, Korea. In the laboratory chamber experiments, the concentrations of the artificial contaminated water were measured in terms of TSS (Total Suspended Solids) and COD (Chemical Oxygen Demand) and compared with each other to evaluate the performance of sand filter layers. In addition, the accumulated weight of pollutant particles clogged in the sand filter layers was estimated. This paper suggests a prediction model for removal of non-point source pollutants with theoretical consideration of the physical characteristics such as the grain-size distribution and composition, and change in the hydraulic conductivity and porosity of sand filter layers. The lumped parameter related with the clogging property was estimated by comparing the accumulated weight of pollutant particles obtained from the laboratory chamber experiments and calculated from the prediction model based on the clogging theory. It is found that the lumped parameter has a significant influence on the amount of the pollutant particles clogged in the pores of sand filter layers. In conclusion, according to the clogging prediction model, a double-sand-filter layer consisting of two separate layers: the upper sand-filter layer with the effective particle size of 1.49 mm and the lower sand-filter layer with the effective particle size of 0.93 mm, is proposed as the optimum system for removing non-point source pollutants in the field-sized artificial rainwater reservoir.

Temperature Performance of Different Pervious Pavements: Rainwater Harvesting for Energy Recovery Purposes

Pervious pavements offer a solution for rainwater runoff treatment in urban areas, combining storm-water management with water reuse purposes when the sub-bases become rainwater reservoirs. Furthermore, the thermal behaviour research into these systems has demonstrated their contribution to palliating the urban heat island effect in the hottest season and to delaying freezing during the coldest season. Recent investigations related to pervious pavements and their sub-bases have enabled the use of these structures combined with Ground Source Heat Pumps (GSHP) in addition to the other well-known applications. The aim of this field study is to investigate the temperature response observations of the water stored in the sub-bases of different pervious pavements under specific conditions, in order to evaluate the possibility of introducing GSHP technology. The base and sub-base temperatures of different types of pervious pavements were monitored during one year and the results obtained show the differences in pervious pavements temperature compared to air temperature over the period of study; and demonstrate that the sub-base is less affected by the air temperature than the base, due to the insulating capacity of pervious pavements. On the other hand, water samples were taken from the different pervious pavement sub-bases in order to assess the water quality deterioration due to the temperatures reached in the sub-base, focused on investigating the presence of Legionella in this particular aquatic environment.

Monitoring and Evaluation of the Thermal Behavior of Permeable Pavements for Energy Recovery Purposes in an Experimental Parking Lot: Preliminary Results

Permeable pavements offer a solution for rainwater runoff treatment in urban areas, combining water management with water reuse purposes when the sealed subbase become rainwater reservoirs. Furthermore, the thermal behavior investigations of these systems have proved their contribution to palliate the urban heat island effect in the hottest season and to delay freezing during the coldest season. Increasing knowledge of heat-transfer mechanisms into the permeable pavements and their subbase has enabled the use of these structures combined with ground source heat pumps (GSHP) in addition to the other well-known applications. The aim of the present study is to investigate the thermal response observations of permeable pavements under specific weather conditions while paying attention to the temperature distribution in the subbase, where rainfall water is stored for others uses, to evaluate the possibility of introducing GSHP technology. The bedding layer and subbase temperature of reinforced grass permeable pavements was monitored during three months in summer 2008, and the preliminary results obtained show the subbase temperature different from the air temperature during the period of the study and demonstrate that the subbase is less affected by the air temperature than the bedding layer because of the insulating capacity of permeable pavements, explained through the heat-transfer processes that take place into the pavements.

On-farm rainwater reservoir system optimal sizing for increasing rainfed production in the semiarid region of Africa

The low productivity of Burkina Faso’s agriculture is mainly due to the shortage of rainwater during the crucial growing period of crops. This study aims to determine the optimal cultivation surface size of the on-farm rainwater reservoir (OFR) by simulating the upland rice water balance and forecasting the yields under different planting dates’ scenario. For this study, important rice crop information and meteorological variables were collected for computing OFR size in three regions at Burkina Faso, including Gaoua, Fada N’Gourma and Dori in the Sudanian, Sudano-Sahelian and Sahelian zones, respectively. Besides, the suitability of upland and paddy rice in the areas under study is also investigated. From the results of this study, it is observed that the upland rice crop is more suitable than paddy rice while considering the regional rainfall pattern. The upland rice production can possibly have two cycles in the Gaoua and Fada N’Gourma regions. For Gaoua, the planting dates for consecutive production are scaled on April 15 to 23 and August 7 to 14, which require 11.10 and 19.17% of the total farm area to be optimally occupied by the OFR, respectively. For the Fada N’Gourma region, the OFR optimal size requires up to 28.39% of the total area for the first crop (upland rice) planted between April 15 and 23. However, the second crop planted between August 7 and 14 must be a low water consumption and short growing stage crop such as tomato. The Dori region can only have a single production cycle corresponding to the OFR cultivation area of 26.17%. As a result, OFR is able to improve the water availability and mitigate the water stress for reaching the potential yield (7 tons/hectare) through supplementary irrigation option. It is expected to substantially increase the crop productivity by using the OFR system in semiarid regions of Africa.

Density-dependent growth performance of Indian major carps in rainwater reservoirs

Summary The study was carried out to evaluate growth performance of Indian major carps at different stocking densities in rainwater reservoirs. In this experiment, the absolute growth performance of Catla catla, Labeo rohita and Cirrhinus mrigala at stocking densities of 5000, 8000 and 11 000 fingerlings per hectare was 377.7, 215.4 and 241.9; 370.2, 186.7 and 219.1; and 306.7, 163.4 and 180.6 g, respectively. The recorded biomass yield at 5000, 8000 and 11 000 fingerlings per hectare was 1035, 1572 and 1573 kg ha−1 per 180 days of culture. The effect of stocking density on production performance (performance index, PI) was highly significant (P < 0.05) at the higher stocking density of 11 000 ha−1, while there was no significant variation between PI at stocking densities of 5000 and 8000 ha−1. This indicates optimum production performance at 8000 ha−1, where yield is significantly higher (P < 0.05) than yield at 5000 ha−1 and almost equal to the yield at 11 000 ha−1. An increase in stocking density from 8000 to 11 000 ha−1, however, showed a sharp decline in average mean body weight of each species, even with supplemental feeding. With an increase in stocking density, the biomass yield increased to an optimum (1572 kg ha−1), with no substantial increase thereafter. Reductions in growth, which occurred at high density, did not appear to be due to poor water quality as the water quality did not differ significantly among various treatments. Thus, the reduced survival and growth at high density appears to be a behavioural interaction or physiological response to density itself.

GOOD REASONS FOR ROOF PLANTING - GREEN ROOFS AND RAINWATER

GOOD REASONS FOR ROOF PLANTING - GREEN ROOFS AND RAINWATER

Maternal care in the bromeliad crab Metopaulias depressus (Decapoda) : maintaining oxygen, pH and calcium levels optimal for the larvae

Harsh physico-chemical conditions during early development may select for parental care. However, no study on the evolution of parental care has focused on the physico-chemical conditions in the environment, the physiological needs of early life stages and the significance of parental care. Early development of the bromeliad crab is completed in small rainwater reservoirs in bromeliad leaf axils. Axils not cared for by mother crabs are acidic, hypoxic and contain very little Ca2+. Maternal care buffers axil water and increases oxygen and Ca2+ availability. Our results show that (a) bromeliad crab larvae die at pH levels usually found in unattended axils, but develop successfully into the first crab stage at the pH typical of cared-for axils; (b) oxygen concentration in unattended axils is below the critical concentration for larvae, but is high enough for normal respiration in cared-for axils; (c) the calcium demand of larvae for moulting and development cannot be satisfied in unattended axils, but is met by the higher calcium content of cared-for axils. Therefore, physicochemical conditions in the bromeliad axil habitat exert strong selection for the maintenance of parental care in the bromeliad crab.