Making Rainwater Harvesting a Key Solution for Water Management: The Universality of the Kilimanjaro Concept

Exploring the spatiotemporal variations in regional rainwater harvesting potential resilience and actual available rainwater using a proposed method framework

Rainwater harvesting potential provides a basis for alleviating regional drought and water shortages. The resilience of rainwater harvesting potential is directly related to the sustainable level of actual available rainwater. Thus, SWAT model was combined with the proposed rainwater harvesting potential evaluation model to quantify rainwater harvesting potential, its resilience and actual available rainwater in the study area. The results showed that: (1) restoration of forest and grass increased the rainwater resource potential in the study area by 12.41 %, especially in the northeast, central and southwest of the study area. Although the surface runoff increased slightly in the past 20 years, it remained stable at 28.62 % of rainwater harvesting potential, which was benefited from the rainwater harvesting potential resilience to maintain the component stability; (2) rainwater harvesting potential resilience in the study area increased from class II to class III, which was closely related to the 17.93 % increase in the resilience intensity of the study area to resist external interference; and (3) surface runoff and net soil moisture content were the main components affecting the spatiotemporal variation of actual available rainwater, and lateral flow was also the main component affecting the spatial variation of actual available rainwater. In the past 20 years, the actual available rainwater has been increasing, and its conversion rate exceeded 89 %. The high level of actual available rainwater has been expanding to the western region with dense grassland coverage. This study provides a scientific basis for clarifying the sustainable utilization level of rainwater.

Synthetic fertilizers alter floral biophysical cues and bumblebee foraging behavior

The use of agrochemicals is increasingly recognized as interfering with pollination services due to its detrimental effects on pollinators. Compared to the relatively well-studied chemical toxicity of agrochemicals, little is known on how they influence various biophysical floral cues that are used by pollinating insects to identify floral rewards. Here, we show that widely used horticultural and agricultural synthetic fertilizers affect bumblebee foraging behavior by altering a complex set of interlinked biophysical properties of the flower. We provide empirical and model-based evidence that synthetic fertilizers recurrently alter the magnitude and dynamics of floral electrical cues, and that similar responses can be observed with the neonicotinoid pesticide imidacloprid. We show that biophysical responses interact in modifying floral electric fields and that such changes reduce bumblebee foraging, reflecting a perturbation in the sensory events experienced by bees during flower visitation. This unveils a previously unappreciated anthropogenic interference elicited by agrochemicals within the electric landscape that is likely relevant for a wide range of chemicals and organisms that rely on naturally occurring electric fields.

A Hybrid Model for Achieving Universal Safe Drinking Water in the Medium-Sized City of Bangangté (Cameroon)

Providing everyone with safe drinking water is a moral imperative. Yet, sub-Saharan Africa seems unable to achieve “safe drinking water for all” by 2030. This sad situation calls for a closer examination of the water supply options for both rural and urban populations. Commonly, two main aspects are considered: (1) behavioural responses to available or potential water supply options, and (2) socio-economic acceptability. These aspects determine the feasibility and the affordability of bringing safe drinking water as a basic good and human right to everyone. There is a broad consensus that achieving the UN Sustainable Development Goal 6.1 is mostly a financial issue, especially in low-income settings. This communication challenges this view as water is available everywhere and affordable treatment options are well-known. It considers the decentralized water supply model as a reference or standard approach in low-income settings rather than as an alternative. Here, the medium-sized city of Bangangté in the western region of Cameroon is used to demonstrate that universal safe drinking water will soon be possible. In fact, during the colonial period, the residences of the elite and the main institutions, including the administrative quarter, churches, and hospital, have been supplied with clean water from various local sources. All that is needed is to consider everyone as important or accept safe drinking water as human right. First, we present a historical background on water supply in the colonial period up to 1980. Second, the drinking water supply systems and water demand driven by population growth are discussed. Finally, a hybrid model for the achieving of universal access to clean drinking water, and preconditions for its successful implementation, are presented. Overall, this communication calls for a shift from safe drinking water supply approaches dominated by centralized systems, and presents a transferable hybrid model to achieve universal clean drinking water.

Application of the Kilimanjaro Concept in Reversing Seawater Intrusion and Securing Water Supply in Zanzibar, Tanzania

There is escalating salinity levels on small islands due to uncontrolled groundwater extraction. Conventionally, this challenge is addressed by adopting optimal groundwater pumping strategies. Currently, on Unguja Island (Zanzibar), urban freshwater is supplied by desalination, which is expensive and energy-intensive. Hence, desalinization cannot be afforded by rural communities. This study demonstrates that the innovative Kilimanjaro Concept (KC), based on rainwater harvesting (RWH) can remediate seawater intrusion in Unguja, while enabling a universal safe drinking water supply. The reasoning is rooted in the water balance of the whole island. It is shown that if rainwater is systematically harvested, quantitatively stored, and partly infiltrated, seawater intrusion will be reversed, and a universal safe drinking water supply will be secured. Water treatment with affordable technologies (e.g., filtration and adsorption) is suggested. The universality of KC and its suitability for small islands is demonstrated. Future research should focus on pilot testing of this concept on Unguja Island and other island nations.

Integrated Water Resource Management: Rethinking the Contribution of Rainwater Harvesting

Rainwater harvesting (RWH) is generally perceived as a promising cost-effective alternative water resource for potable and non-potable uses (water augmentation) and for reducing flood risks. The performance of RWH systems has been evaluated for various purposes over the past few decades. These systems certainly provide economic, environmental, and technological benefits of water uses. However, regarding RWH just as an effective alternative water supply to deal with the water scarcity is a mistake. The present communication advocates for a systematic RWH and partial infiltration wherever and whenever rain falls. By doing so, the detrimental effects of flooding are reduced, groundwater is recharged, water for agriculture and livestock is stored, and conventional water sources are saved. In other words, RWH should be at the heart of water management worldwide. The realization of this goal is easy even under low-resource situations, as infiltration pits and small dams can be constructed with local skills and materials.

Economic and Environmental Assessment of Two Different Rain Water Harvesting Systems for Agriculture

Increasing aridity and subsequent water scarcity are currently among the major problems of agriculture. Rainwater harvesting could represent a way to tackle this issue, and, as a consequence, scientific research has been more and more focused on such topic. On the other hand, few scientific studies related to economic and environmental assessment of rainwater harvesting systems in agriculture are available. The present study carried out an economic and environmental analysis of two different systems for rainwater harvesting: a typical pond and an innovative flexible water storage system (FWSS). The environmental and economic performance of the systems was compared using the Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) methodologies, referring to a functional unit (FU) of 1 m3 of storable water. The FWSS showed better environmental end economic performance than the pond system, resulting with both lower environmental impacts (17.04 g per m3 CO2vs 28.2 g per m3 CO2) and lower costs (16.94 € per m3vs 20.41 € per m3). Moreover, the pond system was more impactful than the FWSS for all the 17 categories investigated. Therefore, the FWSS can be a suitable solution for water harvesting in agriculture sector, showing interesting features for farmers.

A Review of Roof and Pond Rainwater Harvesting Systems for Water Security: The Design, Performance and Way Forward

Rapid urbanization, population explosion and climate change have threatened water security globally, regionally and locally. While there are many ways of addressing these problems, one of the innovative techniques is the recent employment of Sustainable Urban Drainage Systems (SUDS) which include rainwater harvesting systems (RWHS). Therefore, this paper reviews the design and component of two types of RWHS, the namely roof harvesting system (RHS) and the pond harvesting system (PHS). The performance in terms of quantity and quality of collected rainwater and energy consumption for RWHS with different capacities were evaluated, as well as the benefits and challenges particularly in environmental, economic and social aspects. Presently, the RHS is more commonly applied but its effectiveness is limited by its small scale. The PHS is of larger scale and has greater potentials and effectiveness as an alternative water supply system. Results also indicate the many advantages of the PHS especially in terms of economics, environmental aspects and volume of water harvested. While the RHS may be suited to individual or existing buildings, the PHS has greater potentials and should be applied in newly developed urban areas with wet equatorial climate.

Designing the Next Generation of Fe0-Based Filters for Decentralized Safe Drinking Water Treatment: A Conceptual Framework

The ambitious United Nations Sustainable Development Goal for 2030 to “leave no one behind” concerning safe drinking water calls for the development of universally applicable and affordable decentralized treatment systems to provide safe drinking water. Published results suggest that well-designed biological sand filters (BSFs) amended with metallic iron (Fe0-BSFs) have the potential to achieve this goal. Fe0-BSFs quantitatively remove pathogens and a myriad of chemical pollutants. The available data were achieved under various operating conditions. A comparison of independent research results is almost impossible, especially because the used Fe0 materials are not characterized for their intrinsic reactivity. This communication summarizes the state-of-the-art knowledge on designing Fe0-BSFs for households and small communities. The results show that significant research progress has been made on Fe0-BSFs. However, well-designed laboratory and field experiments are required to improve the available knowledge in order to develop the next generation of adaptable and scalable designs of Fe0-BSFs in only two years. Tools to alleviate the permeability loss, the preferential flow, and the use of exhausted filters are presented.

Potential Water Harvesting Sites Identification Using Spatial Multi-Criteria Evaluation in Maysan Province, Iraq

Rainwater harvesting is a promising tool for supplementing surface water and groundwater to overcome the imbalance between water supply and demand under changing climate conditions. Multi-Criteria Evaluation is one of the well-known methods of decision-making. In this study, the geographical information system (GIS)-based Multi-Criteria Evaluation is used to select the optimum rainwater harvesting sites in Maysan province, Iraq. Fuzzy membership is used for standardization of the criteria, and Fuzzy Gamma overlay for a combination of multi-layers using ArcGIS 10.5. Seven criteria layers, including slope, stream order, soil type, precipitation, evaporation, roads, and the Normalized Difference Vegetation Index (NDVI) are derived to identify rainwater-harvesting catchment. The results determined the optimum sites for water storage within the study area. The resultant potential rainwater harvesting catchment map can be used as a reference to enhance the effectiveness of water management, especially in drought-stricken areas that offer significant potential for sustainable agricultural production in the semi-arid region.

Metallic Iron for Environmental Remediation: Starting an Overdue Progress in Knowledge

A critical survey of the abundant literature on environmental remediation and water treatment using metallic iron (Fe0) as reactive agent raises two major concerns: (i) the peculiar properties of the used materials are not properly considered and characterized, and, (ii) the literature review in individual publications is very selective, thereby excluding some fundamental principles. Fe0 specimens for water treatment are typically small in size. Before the advent of this technology and its application for environmental remediation, such small Fe0 particles have never been allowed to freely corrode for the long-term spanning several years. As concerning the selective literature review, the root cause is that Fe0 was considered as a (strong) reducing agent under environmental conditions. Subsequent interpretation of research results was mainly directed at supporting this mistaken view. The net result is that, within three decades, the Fe0 research community has developed itself to a sort of modern knowledge system. This communication is a further attempt to bring Fe0 research back to the highway of mainstream corrosion science, where the fundamentals of Fe0 technology are rooted. The inherent errors of selected approaches, currently considered as countermeasures to address the inherent limitations of the Fe0 technology are demonstrated. The misuse of the terms “reactivity”, and “efficiency”, and adsorption kinetics and isotherm models for Fe0 systems is also elucidated. The immense importance of Fe0/H2O systems in solving the long-lasting issue of universal safe drinking water provision and wastewater treatment calls for a science-based system design.