Water-saving Efficiency Research Articles

Study on the performance temporal variation of rainwater harvesting systems based on the dynamic change of rainfall pattern and domestic water demands

Rainwater harvesting systems (RWHs) in buildings are benefits in alleviating urban water scarcity. However, climate change and changes in building water demand affect the expected performance of RWHs over their life cycle. Previous studies have only focused on the adaptability of RWHs to climate change without considering the changes in building water demand. To address this issue, this study explores the impact of combined changes in precipitation patterns and domestic water demand on the water-saving efficiency of RWHs over their 25-year life cycle based on historical observations. Three cities in Japan were selected as case studies. The results indicate that during 25-year life cycle of RWHs, precipitation in different cities in Japan shows an increasing trend, while domestic water demand shows a decreasing trend. Such trend resulted in a change of -2.90–4.02% in the water-saving efficiency of the established RWHs and a change of -2.90–3.82% in the theoretical optimal water-saving efficiency, and these effects were greater in RWHs in buildings with high non-potable water demands. Therefore, RWHs in buildings with low non-potable water demand can appropriately reduce the rainwater tanks, while RWHs in buildings with high non-potable water demand must increase the rainwater tank size to eliminate this adverse effect. Furthermore, both reductions in domestic water demand and increases in precipitation have a positive effect on the water-saving efficiency of RWHs. However, when both domestic water demand and precipitation increase or decrease simultaneously, the change in water-saving efficiency of RWHs is related to the non-potable water demand of the building. This study can provide data support and theoretical evidence for the further implementation of RWHs under climate change, and can help stakeholders to optimize and update RWHs to ensure system feasibility.

Regionalization of environmental and economic performances of rainwater harvesting systems

Study regionBeijing Region Study focusLimited studies have yet been done on regionalization of multi-performances of rainwater harvesting systems (RHS). In this study, the daily rainfall records from 77 stations are used, and a hydro-economic model is adopted to examine regional water saving, stormwater control and economic performances of RHS by proposing a regionalization approach. New hydrological insights for the regionHigher water saving efficiency (WSE) and reliability (R) of RHS are linked with lower water demand, larger tank size and greater rainfall conditions. Differently, higher stormwater capture efficiency (SCE) is related to higher water demand, larger tank size and lower rainfall. The WSE and R of RHS demonstrate substantial regional differences; their maximized obtainable values closely depend on water demand scenarios and range from 9% to 99%, with smaller values in western mountain area but larger values in northeast suburban and central urban areas. The maximum obtainable values of SCE range from 61% to 100%, with higher values in western mountain area, but lower values in northeast suburban and central urban areas. A 10 m3 tank size can provide the highest benefit-cost ratio of RHS across the Beijing region. The regionalization approach proposed is a useful guidance for the implementation of RHS and sustainable urban water management, and thus it has the potential for wide uses in other regions with high rainfall gradients.

Multi-Objective Performance of Detention Basins and Rainwater Harvesting Systems Using Real-Time Controls with Rainfall Forecasts

Climate change and an increase in urbanization are severely testing urban drainage systems; at the same time, population growth is leading to an increase in demand for water resources, while climate change is more likely to reduce the amount of water that is available to meet this demand. The present study finds a solution to both problems by assuming a hybrid use of detention basins, i.e., providing a real-time control system (RTC) for the outfall discharge managed according to the rainfall forecast and the water level in the tank, to reuse rainwater for non-potable use and, at the same time, to guarantee the hydraulic protection of the downstream system. Twenty-seven scenarios were simulated using the numerical model SWMM 5.1, assuming different types of controls on the discharge. The simulations show a non-potable water-saving efficiency from a minimum of 32% to a maximum of 90%, and the reduction in volume discharged is between 11% and 31%, while the peak flow rate varies more significantly depending on the type of control used. These results highlight the detention basins’ potential deriving from the hybrid use of this system with rainwater harvesting systems.

The Effect of the Depth of Soil Moisture on the Growth and Development of Cherry Seedlings

Background: For the first time in the conditions of the Volgograd region, new knowledge was obtained, which made it possible, taking into account the changes in the morphology of the root system occurring during the formation of seedlings, the orientation of physiological processes and the biological needs of plants for their optimization, to justify a differentiated water-saving drip irrigation regime in combination with fertilizing vegetating plants, providing high-quality annual sweet cherry seedlings with high economic and water-saving efficiency, environmental tolerance. Methods: The experimental part of the work was carried out in the laboratory of breeding, seed production and nursery breeding 2017-2021 years. The productivity of the variety-rootstock combination was calculated relative to biometric parameters: crown projection area (S), crown volume (V), stem cross-sectional area (S). Result: In the course of the work, methods of watering stone crops, in particular cherries and their effect on survival, growth and development of seedlings in the nursery were studied. The scheme of experiments provides for an assessment of the influence of the water regime of the soil on the formation of the height of the central stem, the root system and the yield of seedlings of class 1 according to the variants of the experiment. Their values were greater than in the control, respectively, by 21 and 17 cm, 24-32%. At the same time, the yield of first-class seedlings in the third variant exceeds the second variant by 6%. According to the results of the conducted studies, the option of maintaining soil moisture at least 80% of the lowest moisture capacity during the adaptation period of the graft with a rootstock in a layer of 0.2 meters, followed by an increase in the soaking depth to 0.4 meters, proved to be the best. In the phase of the transition of seedlings to the dormant period, the pre-watering soil moisture should be maintained at least 70%.

Simulating drip irrigation in large-scale and high-resolution ecohydrological models: From emitters to the basin

Drip irrigation is deemed as a solution to the water conflict between agricultural and ecological needs in arid regions, but assessing hydrological impacts of drip irrigation remains challenging. This study developed a new approach to simulating drip irrigation at a basin scale, with the configuration of irrigation system explicitly represented and the emitter-scale wetted soil volume directly modeled, and incorporated the approach into HEIFLOW, a fully distributed and physically based ecohydrological model. The improved model, named HEIFLOW-drip, was used to study the potential implementation of drip irrigation in the Zhangye basin in Northwest China. Due to the recycling effect of irrigation return flow, the basin-scale water-saving efficiency (WSE) of drip irrigation fully implemented in the irrigated farmlands is 16.8%, less than half of its field-scale WSE (36.5%). This discrepancy indicates that accounting the water saved in fields may lead to notable overestimation of the basin-wide water saving by drip irrigation in basins with strong surface water-groundwater interactions. If fully implemented, drip irrigation would significantly alter the regional water balance, increasing the stream outflow by approximately 30%, while causing a decline in groundwater level. This tradeoff can be alleviated by tuning the management parameters of drip irrigation, which can achieve a synergistic effect of increasing the streamflow while preventing dramatic groundwater depletion. Another effective strategy is to implement drip irrigation in part of the basin. Given the intricate impacts of drip irrigation on hydrological processes, the determination of the scale and location of drip irrigation should be thought through at the basin level. Further analyses indicate the importance of proper management of the water saved by drip irrigation, which is crucial to prevent the paradox of irrigation efficiency. The findings of this study have great implications for addressing the complex water-food-ecosystem nexus in arid endorheic river basins.

Water–energy nexus: The coupling effects of water and energy policy applied in China based on a computable general equilibrium model

China has implemented a number of national and regional water and energy policies to achieve its goals of carbon emissions (CE) reduction, energy saving, and water conservation. Given its high energy and water resources interdependence, a framework is needed that can provide both a unified and systematic assessment of these. This study investigates the effects of coupling China's energy tax and water fee policies using a recursive dynamic computable general equilibrium model. Several possible scenarios are simulated. The simulation results show that the water fee promotes water conservation, but its effect is limited at China's current water fee level. The energy tax is shown to be more effective in improving water-saving efficiency. Under the maximum energy tax scenario (EH), total energy and industrial water demand fall by 10.45% and 3.82%, respectively, compared with 0.59% and 0.72%, respectively, under the maximum water fee scenario (W8). Furthermore, the energy tax is more conducive to China's energy conservation and CE reduction (CER) targets than the water fee, but raising both energy taxes and water fees can have a significant impact on energy conservation and CER. In the scenario going from a low energy tax (EL) to a high-energy tax (EH), the reduction in primary energy production increases from 8.36% to 19.16%, while CE also drop significantly, going from 5.59% to 16.71%; however, In the scenario going from the low water fee (W2) to the high-water fee (W8), the reduction in primary energy production only changes from 0.24% to 0.43%, and CO2 reduction from 0.35% to 0.61%. Meanwhile, the mixed water-energy scenario shows a spill over effect, with the CE and energy savings management goals requiring less GDP loss than water or energy policies implemented in isolation. Ultimately, the results show that even when combined, relying solely on existing water and energy tax policies will be insufficient to meet China's water-saving targets without other environmental policies. The key to overcoming energy and water constraints is to increase water and energy efficiency year after year. This will enable China to achieve its CER target and the 14th Five-Year Plan water savings target. Thus, the synergistic effect of water conservation and energy saving can be realised simultaneously when the CER and energy consumption structure improve, which is crucial for developing an effective environmental policy strategy.

Analisis Tarif Air PDAM Untuk Kelayakan Penerapan Sistem Pemanenan Air Hujan pada Skala Rumah Tangga

The limited availability of clean water is a problem that often occurs lately. Water use continues to increase due to population growth and technological developments. The availability of abundant rainwater and the application of a rainwater harvesting system are alternatives for water fulfillment as water supplies are limited. Rainwater harvesting system performance simulation modeling is essential in deciding the suitability of rainwater harvesting systems. In this study, the rainwater harvesting system simulation modeling was carried out using the Yield Before Spillage (YBS) algorithm in 3 cities in Indonesia (Palembang City, Bogor City, and Mataram City). This assessment considers 5 combinations of demand, 5 combinations of catchment area, 5 tank capacities, and 3 applicable water rates, resulting in 1,875 different value configurations. The performance and potential assessment of the rainwater harvesting system are determined by Water Saving Efficiency and Timetric Reliability, while the financial assessment is determined using the payback period and benefit-cost ratio. Benefits are derived from the potential for water savings with a rainwater harvesting system which is converted into financial savings according to the prevailing water rates and costs are determined based on the initial installation costs of the rainwater harvesting system. The results of this study indicate that the city of Bogor with an average rainfall of 3805.95 mm/year has the highest WSE rate of 100% and the fastest payback period is 4 years. Palembang City with an average rainfall of 2551.57 mm has the highest WSE rate of 99,273% and the fastest payback period is 5.42 years. Mataram, with an average rainfall of 1661.79 mm, has the highest WSE rate of 91.752% and the fastest payback period is 8.17 years. Topographical conditions and rainfall greatly affect the performance of the rainwater harvesting system.

Climate Change Impacts on Rainwater Tank’s Potential Water Savings, Efficiency and Reliability Presenting Relationship Between ‘Seasonality Index’ and Water Savings Efficiency

The paper presents potential impacts of climate change on rainwater tanks outcomes such as water savings, reliability and water savings efficiency under two projected climate change scenarios; RCP4.5 and RCP8.5 utilising a case study using rainfall data from four stations within the city of Brisbane, Australia. Historical rainfall data were collected from the Australian Bureau of Meteorology website for the selected stations. Projected daily rainfall data were collected from Australian government data portal for the same stations within Brisbane. Using an earlier developed daily water balance model, eTank potential annual water savings were calculated for several weather and climate change scenarios with varied roof areas and rainwater demandValues of ‘Seasonality Index (SI)’, a commonly used factor representing rainfall variability within a year, were explored to validate earlier developed relationships between SI and water savings efficiency through rainwater tanks. It is found that in most cases water savings in future periods are expected to decrease and such decrease is not necessarily attributed to the expected decrease in rainfall amounts in future, rather also affected by future reductions in rainwater tank reliability. Linear relationships between potential future water savings and reliabilities for all the stations are found. Relationship between SI and water savings efficiency was established, and it is found that the relationship slightly varies with an earlier developed relationship using historical data. Compared to earlier established relationship, for lower SI values water savings efficiency is expected to become better, while for higher SI values the water savings efficiency is expected to become worse. Also, an increase of roof area from 100 m2 to 200 m2 will cause an average increase of water savings efficiency by 25% and an increase of rainwater usage from 200 L/day to 300 L/day will cause an average increase of water savings efficiency by 20%.

Effects of kaolin particle film coatings on the water-saving efficiency and fruit quality of Cabernet Sauvignon (Vitis vinifera L.) grape plants in the Ningxia region of China

Effects of kaolin particle film coatings on the water-saving efficiency and fruit quality of Cabernet Sauvignon (Vitis vinifera L.) grape plants in the Ningxia region of China

Water quality and interaction between groundwater and surface water impacted by agricultural activities in an oasis-desert region

A comprehensive understanding of groundwater dynamics and its interaction with surface water under the influence of agricultural activities is essential for local agriculture, ecology and resident in arid regions, which is poorly understood in arid oasis-desert region. In our study, with emphasis on a comparison of hydrogeochemical characteristics between the oasis (irrigated) and desert (non-irrigated) areas, the water quality and groundwater-surface water interaction of a typical oasis-desert system with a rapid irrigation agriculture development were examined to clarify the effects of agricultural activities on groundwater level and quality using stable isotopic and hydrochemical data of 83 water samples. Results showed that cultivated land area increased by 121.8 % (732.4 km2) during 2000 to 2020, mainly transferring from grassland and bare land. Groundwater EC ranged from 786 to 49,400 μS/cm, with weakly alkaline. Shallow groundwater had a much higher EC than other water components. Stable isotopic and EC values of shallow groundwater in the non-irrigation areas were much greater than those in the irrigation areas, whereas middle groundwater isotopic values were more depleted in the desert than in the oasis. Shallow groundwater EC value was lower in summer, middle groundwater had higher EC in summer. Streamflow and confined water in the study area are suitable for agricultural irrigation, but phreatic water in the oasis is generally not suitable for irrigation at present. The groundwater chemistry was mainly controlled by strong evaporation, dilution, mixing, water-rock interaction and agricultural drainage. Groundwater in the irrigation areas was recharged by ephemeral runoff seepage, irrigation return flow and subsurface lateral inflow. Long-term development of irrigation agriculture (large-scale land reclamation, irrigation and groundwater pumping) in arid region has caused groundwater level decline and salinization, with a strong interaction between phreatic water and surface water. Hence, decreasing irrigation area and groundwater exploitation, carrying out gradual ecological restoration, improving water-saving efficiency and agricultural drainage system would be the viable method to restore groundwater and maintain the oasis-desert ecosystem coexistence in arid regions in the context of climate change.

Climate Change Impacts on ‘Seasonality Index’ and its Potential Implications on Rainwater Savings

Seasonality Index (SI) is commonly used to define rainfall variability within a year for a locality, which has got significant impact on the water resources planning and management. Both the longer periods of dry and wet conditions are reflected by SI value. As SI is calculated using historical rainfall data, a historical average value is represented for a locality. However, with the emerging impacts of climate change SI values based on historical data are likely to change. This paper presents expected changes in future SI values for the largest city of Australia (Sydney) based on projected future rainfall scenarios for the city. The paper further illustrates potential water savings through rainwater tanks under projected climate change scenarios using an earlier developed daily water balance model, eTank. For the simulations of potential water savings through rainwater tanks, projected daily rainfall data was collected from Australian government data portal for four stations within Sydney. Future potential rainwater savings efficiencies were correlated with the corresponding SI values. It is found that such correlation closely matches with an earlier developed correlation using past historical data, however the future water savings efficiency will be slightly lower than the past water savings efficiency.

A Type of “Bubble” Water-saving Faucet

At present, many places are seriously short of freshwater resources. Thus, saving water is the universal responsibility of contemporary citizens. Now faucet products such as ordinary washing nozzle, kitchen nozzle, face-washer nozzle, bathtub nozzle and washing machine nozzle are widely used in urban and rural households. Most have poor water-saving abilities, and much water is wasted through daily washing. Our bubble-type water-saving device is a brand-new water-saving device with a simple structure and low cost. It uses the Bernoulli principle and the bubble atomizing principle to inhale air naturally in water flow to atomize water flow. It can help achieve more than 50% water-saving efficiency in daily washing behavior.

Water Content Variations and Pepper Water-Use Efficiency of Yunnan Laterite Under Root-Zone Micro-Irrigation.

Understanding the water content variations in Yunnan laterite (red loam soil, SR) in small-scale environments and exploring the potential for crop water-use efficiency (WUE) improvement are crucial for improving water-saving irrigation technologies used in greenhouse agriculture in Yunnan, China. In this study, a closed-loop model for calculating soil water in greenhouse potted cultivation was established based on water conservation. A Yunnan SR, yellow sand soil (SY), and a 1:1 SR–SY mixture (SM) subjected to root-zone micro-irrigation or surface-drip irrigation were experimentally examined to compare their water content variations and pepper WUEs. The results showed that the soil type and soil type–irrigation mode interaction had significant effects on both soil evaporation and pepper WUE, and that the variations in soil evaporation with respect to time can be expressed using a cubic polynomial function. In small-scale greenhouse cultivation, IG has good water-saving potential and is suitable for the SR (which has a better water-retention capacity), whereas IM is more suitable for the SY (which has a better water-penetration capacity). Mixing certain proportions of the SY into the SR will effectively impact the water content variations and crop WUE and provide opportunities for further improving the water-saving efficiency.

An IoT-based intelligent irrigation system with data fusion and a self-powered wide-area network

Water resources have a great influence on human society, but saving water in irrigation still remains a challenge. This article proposes an intelligent irrigation system that integrates a data fusion model and a long-rang (LoRa) network for optimizing the watering schedule. A data fusion model is proposed, which first adopts the long short-term memory (LSTM) network to simulate and predict the proper watering demands by integrating multi-source heterogeneous data, that is, historical weather data, user irrigation logs, weather forecasts, and online monitoring sensor data. A self-powered wide-area network is implemented and deployed by using LoRa to facilitate multiple Internet of Things (IoT) application scenarios. It includes a gateway and two types of nodes: a valve node and a sensing node. The node is capable of energy autonomy through the scheme of waterflow-based power generation, thus realizing maintenance-free throughout the life cycle. A cloud platform is designed to provide network management, intelligent irrigation control, and the interface of the mobile application. The proposed system is evaluated through a case study of landscape watering. On average, the proposed system achieves a water-saving efficiency of 94.74% compared with the conventional manual setting solutions.

Plant water stress monitoring and control system

Precision irrigation is an important component of the water-saving approaches in agriculture and is one of the methods for increasing water-saving efficiency. Detecting water stress in crops accurately is the basis of precision irrigation techniques. In this study, the crop water stress monitoring system was developed to detect the acoustic emission (AE) of plants, associating the three factors of soil, crops, and weather in real-time. The automatic monitoring system, which was developed using the virtual instrument platform, not only affects the water stress and the drought of the atmosphere but can also be used to control the greenhouse environment automatically. The substance subjected to testing was a potted tomato plant (Lycopersicon esculentum). Environmental parameters are monitored in this system using a virtual instrument data acquisition system based on Peripheral Component Interconnect - Data acquisition (PCI-DAQ). The AE sensor was used to fix tomato stems at 1/3 and 2/3 of their overall height in order to detect AE information, which serves as an indirect indicator of the plant's water condition. This system, which could test and record water requirement information for the crops, has been demonstrated to be stable, nondestructive, and easily manipulable. The results showed that the cohesion between water molecules was weak under water stress conditions. The water flow fracture of the conduits resulted in cavitation by rapidly expanding gas bubbles. The cavitation event caused a rapid relaxation of the liquid tension that produced an AE of energy. It was found that crop hydraulic structure and anti-drought indicators were correlated with AE, which resulted from crop adaptation to the environment. The counts of AE change regularly, according to the variation of the environment's temperature, humidity, carbon dioxide consistency, and transpiration. Based on the relationship between AE and crop water stress conditions, the mathematical model of precision irrigation was obtained. As producing AE is a complex biological process, the future work is to build the different crops' information models in different growth periods. The data acquisition based on the AE information should be researched further.

Dimensionless parameter method for evaluating decentralized water reuse systems in buildings

• Propose a regionalization method to design RWHs, GWRs, and HRGs. • Obtain the design curves under the stable and seasonal water demand scenarios. • The best scenarios and configurations of RWHs, GWRs, and HRGs are discussed. • GWRs are not recommended to implement in the seasonal water demand buildings. The performance of the decentralized water reuse systems that are widely implemented for the conservation of building water is affected by various characteristics, such as the location and type of building. Generalized methods to evaluate and compare different system configurations under various scenarios are currently lacking. Previously devised methods have focused on specific parameters describing buildings and are therefore not suitable for regionalized application. This study proposes a dimensionless parameter method for the evaluation of three decentralized systems in buildings with stable and seasonal daily non-potable water demands: rainwater harvesting systems (RWHs), graywater recycling systems (GWRs), and hybrid rainwater-graywater systems (HRGs). Japan was selected as a case study to illustrate the feasibility of this method. The results indicate that the favorable precipitation patterns in Japan support the use of RWHs rather than GWRs for conserving water, especially in buildings with seasonal daily non-potable water demands. Upgrading the existing systems to HRGs when RWHs and GWRs cannot meet the demand can increase the maximum water-saving efficiency by 40%. Thus, the method can effectively determine the optimum scenarios and configurations of RWHs, GWRs, and HRGs and provide policy guidance for the regional implementation of decentralized water reuse systems.

Ecological balance model of effective utilization of agricultural water resources based on fractional differential equations

Abstract Water is a key factor that controls the evolution of the ecosystem and restricts social and economic development. The rational allocation of water resources is the basis for the basin's sustainable use of water resources. The article uses fractional differential equations to discuss the increasingly prominent contradictions between supply and demand of agricultural water resources, serious pollution and overexploitation, the decline in groundwater level and water quality, low agricultural water efficiency, and serious waste from the perspective of sustainable development. Second, the article classifies the index system of the water resources carrying capacity evaluation model. Finally, model the resource balance of water supply and water demand in the irrigation area. The study found that the water quantity analysis and determination of the irrigation area will have important guiding significance for implementing the irrigation area's continued construction and water-saving transformation. The allocation and utilization of water resources in farmland irrigation areas will tend to be rationalized. This will greatly improve the water-saving efficiency of irrigation districts.

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.

Water-Saving Efficiency and Inequality of Virtual Water Trade in China

Virtual water trade is widely considered as a potential method to solve local water shortage and unequal distribution. However, limited research investigated water-saving efficiency and water inequality of inter-provincial virtual water trade. In this study, we sought to explore this issue within China based on the 2015 input-output data. A multi-regional input-output model and a modified input-output model were used to estimate the virtual water trade and its impact on water-saving and water inequality. Our results suggest that: (1) The total virtual water flow across the country is 200.03 × 109 m3, which accounts for 32.77% of water withdrawal. The agriculture sector contributes the highest proportion (73.99%) to virtual water flow. (2) Virtual water trade could decrease water withdrawal by 446.08 × 109 m3 compared with withdrawal under no-trade situation at a national level, and 22 provinces could gain benefits through inter-provincial trade with a positive water-saving efficiency index. (3) Virtual water trade also causes water inequality, which exacerbates water scarcity of exported provinces, especially in northwest provinces. (4) There is a conflict between water conservation and water inequality, but different provinces show significant heterogeneity.

Optimization of rainwater harvesting system design for smallholder irrigation farmers in Kenya: a review

Abstract The adverse effects of climate change on agriculture have been felt across the globe. Smallholder farmers in sub-Sahara Africa are particularly more vulnerable to the effects of climate change leading to loss of income and livelihood thus affecting global food security. Rainwater harvesting (RWH) is emerging as a viable option to mitigate the negative effects of climate change by supporting rain-fed agriculture through supplemental irrigation. However, smallholder farmers are still grappling with a myriad of challenges hindering them from reaping the benefits of their investment in RWH systems. This review explores some of the factors behind the poor performance of RWH systems in Kenya and also seeks to suggest techniques that can be applied to optimize the design parameters for improved performance and the adoption of RWH systems. According to the review, RWH has the potential to mitigate the adverse effects of climate change among smallholder farmers. It allows for crop production beyond the growing season through supplemental irrigation. However, their impacts have been minimal due to the consistent poor performance of RWH systems. This is attributed to inefficiencies in design and construction brought about by lack of required technical skills among RWH system designers and implementers. Proper design and implementation are therefore paramount for better performance and adoption of RWH systems in the region. This will ensure that RWH systems are reliable, technically and economically feasible as well as possess a desirable water-saving efficiency.