Effect of roof size on the rainwater harvesting tank sizes and performances using Tangki NAHRIM 2.0

Global warming and increasing population have direct impacts on water demand all over the world. Usage of potable water in Malaysia is high if compared with other countries and the source of potable water is mainly surface water. Rainwater harvesting is one of the popular alternatives to water resources around the world. However, even Malaysia is a country with an abundance of rainfall, rainwater harvesting is still unpopular. Different size of houses has different roof sizes which will subsequently require different sizes of rainwater tanks. This study utilized Tangki NAHRIM 2.0 (TN2); a web application to determine the optimal tank size for a rainwater harvesting system for five different roof sizes for non-potable demand. TN2 simulation uses a daily water balance model with rainfall input from a built-in database by adopting the yield-after-spillage (YAS) convention. The optimum rainwater tank sizes for five different roof sizes are found to be between 2.6 m3 and 3.8 m3 with water-saving efficiency values between 59% to 76.2% and 30.9% to 53.9% for storage efficiency. A bigger tank size offers higher watersaving efficiency but with lower storage efficiency. The output will be useful for the application of RWHS to residential houses.

Dual Benefit of Rainwater Harvesting—High Temporal-Resolution Stochastic Modelling

The objective of the presented study was to develop a high-temporal-resolution stochastic rainwater harvesting (RWH) model for assessing the dual benefits of RWH: potable water savings and runoff reduction. Model inputs of rainfall and water demand are used in a stochastic manner, maintaining their natural pattern, while generating realistic noise and temporal variability. The dynamic model solves a mass-balance equation for the rainwater tank, while logging all inflows and outflows from it for post-simulation analysis. The developed model can simulate various building sizes, roof areas, rainwater tank volumes, controlled release policies, and time periods, providing a platform for assessing short- and long-term benefits. Standard passive rainwater harvesting operation and real-time control policies (controlled release) are demonstrated for a 40-apartment building with rainfall data typical for a Mediterranean climate, showing the system’s ability to supply water for non-potable uses, while reducing runoff volumes and flows, with the latter significantly improved when water is intentionally released from the tank prior to an expected overflow. The model could be used to further investigate the effects of rainwater harvesting on the urban water cycle, by coupling it with an urban drainage model and simulating the operation of a distributed network of micro-reservoirs that supply water and mitigate floods.

Private assets for public benefit: the challenge of long-term management of domestic rainwater tanks

This study explored the relationship private landowners have with their domestic rainwater tank and how that relationship influences the reliability of privately operated rainwater tanks for long-term performance and delivery of service. It found that tank owners generally placed a high value on their tank, desired to have them fully operational and made a reasonable effort to keep them functioning. However, the frequency and extent of maintenance action and effort was variable, and in the context of a private residence, rainwater tanks were typically afforded a low relative priority for repair when compared with other residential assets. This low relative priority could be a primary driver for the reported delay between when a fault occurs with the tank and when it is repaired. This ‘repair lag’ means that a portion of domestic rainwater tanks are likely to be non-operational at any one time. When planning a decentralised system for the management of stormwater, redundancies should be included to cover these gaps in service delivery. It is also recommended that programmes that support private landowners to maintain their rainwater tanks are implemented to minimise repair lag.

ANALISIS PENERAPAN SISTEM RAINWATER TANK DI PERUMAHAN CITRA INDAH BATAM CENTER

Perkembangan penduduk di kota Batam mengakibatkan peningkatan frekuensi terjadinya banjir yang terjadi terutama di Perumahan Citra Indah, Batam Center. Untuk mengatasi masalah yang timbul akibat peningkatan frekuensi terjadinya banjir, maka dilakukan analisis penerapan sistem rainwater tank pada kawasan perumahan. Penelitian ini bertujuan untuk mengetahui perencanaan raintwater tank dan mengetahui jumlah air dan biaya yang dihemat dengan sistem rainwater tank untuk kawasan perumahan Citra Indah, Batam Center. Penelitian ini menganalisis kebutuhan tanki yang diperlukan untuk 4 tipe rumah di perumahan Citra Indah. Data perumahan diperoleh dari PT Bangun Arsikon Batindo dan data curah hujan dari Badan Meteorologi, Klimatologi dan Geofisika (BMKG) Kota Batam. Metode perhitungan dengan menggunakan curah hujan andalan 80% berdasarkan curah hujan tahun 2010-2019 dan luas atap rumah sebagai luas penangkapan. Hasil analisa penerapan sistem rainwater tank di perumahan Citra Indah, untuk tipe rumah 120/162 membutuhkan tanki dengan volume 10,45 m3, tipe rumah 103/120 membutuhkan tanki dengan volume 9,72 m3, tipe rumah 78/105 membutuhkan tanki dengan volume 9,00 m3 dan tipe rumah 50/90 membutuhkan tanki dengan volume 8,79 m3. Penerapan sistem tersebut dapat menghemat penggunaan air sebesar 7,344 m3/bulan dan Rp 705.024/tahun.

Economic Feasibility Analysis of Rainwater Harvesting System at Typical Public Buildings in Guangzhou

Objectives : Rainwater harvesting (RWH) is one of the most promising alternative water sources, since rainwater can easily be collected and used without significant treatment for non-potable purposes. However, the economical viability of these systems is not always assured. The objective of this study is to assess the potential water saving and financial performance of an RWH systems for a typical multifunctional building (with a rooftop area of 2,725 m2) in Guangzhou, China.Methods : The water saving and economic feasibility of the RWH system were examined using a yield after supply model for fourteen rainwater tank schemes (from 1 m3 to 30 m3).Results and Discussion : According to the simulation results, an annual potable water saving of 3,923.56 m3 can be achieved and a corresponding annual revenue of 11,496.04 CNY can be obtained from the RWH system. The economic viability expressed by benefit cost ratio is 1.50 and by payback periods are within 6.26 year, respectively. Sensitivity analysis indicates that the water price is the most important factor affecting the economic viability of an RWH systems. The widespread implementation of rainwater harvesting systems in the public buildings will not only lead to economic savings, but also go further to relive pressure on urban drainage systems and natural water body. Therefore, the actual benefits achieved by a RWH system will be greater than we predicted in current study.Conclusions : These results demonstrating that the application of RWH system is a very promising adaptation strategy for coping with the water crisis and climate change in urban areas of southern China.

Hydrogeological characterization and groundwater quality assessment in an atoll island (Magoodhoo Island of Faafu Atoll - Maldives)

<p>Although freshwater is a vital resource for domestic and productive purposes, it is a very limited and vulnerable resource on atoll islands. Besides precipitations, on coral atolls groundwater is the only source of fresh water, usually extending below sea level in the form of a thin fresh water lens. Several possible environmental hazard can affect the availability of the resource, ranging from salinization induced by overexploitation to deterioration induced by unsustainable land use. Therefore, it becomes important to understand and characterize atolls’ islands aquifers and identify sustainable and hazardous practices to support a wise and farsighted resource management.</p><p>In this work a detailed characterization of the aquifer of Magoodhoo Island (Faafu Atoll – Maldives) is performed, through a hydrogeological mapping and groundwater quality characterization.</p><p>The Magoodhoo Island, with an area of 0.213 km<sup>2</sup>, is a typical and representative native inhabited island (c.a. 850 people) not affected by intense tourist traffic.</p><p>In order to collect topographic data, a drone survey was performed, with a fly altitude set at 80 m a.s.l. to reach a 4 cm ground pixel resolution obtaining a Digital Elevation Model (DEM), with a resolution of 10 cm.</p><p>Groundwater depth (m a.s.l.) was measured in 37 monitoring wells using a water level dipper to obtain a piezometric map of the aquifer. Furthermore, two CTD-diver were used to measure groundwater depth in a monitoring well and tidal oscillation of the sea level simultaneously with a time-resolution of 15 minutes for 5 days.</p><p>Groundwater quality data were collected in 36 monitoring point, including a rainwater tank and analysed for physico-chemical parameters including water temperature  (T), electrical conductivity (EC), pH, dissolved oxygen (DO), and DO saturation (DO%), major ions (Cl, NO<sub>3</sub>-N, NO<sub>2</sub>-N, NH<sub>4</sub>-N, total phosphorus (TP), Si, SO<sub>4</sub>, Ca, Mg, Na, Sr, and K) and metals/semi-metals (As, Pb, Ni, Fe, Mn and Zn).</p><p>Results show that groundwater depth varies spatially from around 1 m a.s.l. in the north-eastern part (ocean side) to -1.2 m a.s.l. in the central-western part. On the time scale, a good correlation between groundwater level and tidal fluctuations is observed and a tidal lag of about 3.5 hours was determined through a cross-correlation analysis.</p><p>Groundwater quality data highlighted different pollution point sources. The main impact on water quality was related to domestic activities producing a great amount of organic matter and wastewater. Other cases of local pollution were identified and associated to farm (poultry) and gardening activities (fertilization).</p><p>This study allowed for an in-depth knowledge of the Maghoodoo island aquifer system, which can be extended to other Maldivian and atoll islands constituting a valuable support for future water resource planning and management.</p>

Potential for Potable Water Savings Due to Rainwater Use in a Precast Concrete Factory

The objective of this paper was to assess the potential for potable water savings due to rainwater use in a precast concrete factory in southern Brazil. The economic feasibility and the rainwater quality were also assessed. The current water consumption, future water demand, and rainwater demand in the factory were estimated. The future demand considered was two times higher than the current water consumption since there were plans to increase the production. Three scenarios were then simulated using the computer programme Netuno. The ideal rainwater tank capacity, the potential for potable water savings, and the economic feasibility analysis for each scenario were estimated. Samples of rainwater were collected in the factory and tested for quality for manufacturing precast concrete. For a rainwater tank capacity equal to 25,000 L, the potential for potable water savings for the first scenario was 55.4%, but the first scenario was considered economically unfeasible. For the same tank capacity, the second and third scenarios presented viable results regarding potable water savings and payback. As for the rainwater quality, it was proven to be adequate for manufacturing precast concrete. The main conclusion was that rainwater can be used to manufacture precast concrete in the factory studied herein.

Rainwater Harvesting Potentials in Commercial Buildings in Dhaka: Reliability and Economic Analysis

Despite numerous studies on residential rainwater tank, studies on commercial rainwater tank are scarce. Corporate authorities pay little heed on this sustainable feature. With the aim of encouraging corporate authorities, this study presents the feasibility and economic benefits of rainwater harvesting (RWH) in commercial buildings in the capital city of Bangladesh, where water authority struggles to maintain town water supply. The analysis was conducted using a daily water balance model under three climate scenarios (wet, dry and normal year) for five commercial buildings having catchment areas varying from 315 to 776 m2 and the storage tank capacity varying from 100 to 600 m3. It was found that for a water demand of 30 L per capita per day (lpcd), about 11% to 19% and 16% to 26.80% of the annual water demand can be supplemented by rainwater harvesting under the normal year and wet year climate conditions, respectively. The payback periods are found to be very short, only 2.25 to 3.75 years and benefit–cost (B/C) ratios are more than 1.0, even for building having the smallest catchment area (i.e., 315 m2) and no significant overflow would occur during monsoon, which leads to both economic and environmental benefits. Though the findings cannot be translated to other cities as those are dependent on factors like water price, interest rate, rainfall amount and pattern, however other cities having significant rainfall amounts should conduct similar studies to expedite implementations of widescale rainwater harvesting.

Potential for Potable Water Savings Due to Rainwater use in a Precast Concrete Factory

The objective of this paper is to assess the potential for potable water savings due to rainwater use in a precast concrete factory in southern Brazil. The economic feasibility and the rainwater quality were also assessed. The current water consumption, future water demand and rainwater demand in the factory were estimated. The future demand considered was two times higher than the current water consumption since there are plans to increase the production. Three scenarios were then simulated using the computer programme Netuno. The ideal rainwater tank capacity, the potential for potable water savings and the economic feasibility analysis for each scenario were estimated. Samples of rainwater were collected in the factory and tested for quality for manufacturing precast concrete. For a rainwater tank capacity equal to 25,000 litres, the potential for potable water savings for the first scenario was 55.4%, but the first scenario was considered economically unfeasible. For the same tank capacity, the second and third scenarios presented viable results regarding potable water savings and payback. As for the rainwater quality, it was proven to be adequate for manufacturing precast concrete. The main conclusion is that rainwater can be used to manufacture precast concrete in the factory studied herein.