Biodiversity of Vegetation and Flora in Tropical Africa

Introduction With increasing global population, the gap between the supply and demand for water is widening and is reaching such alarming levels that in some parts of the world it is posing a threat to human existence. Scientists around the globe are working on new ways of conserving water. It is an opportune time, to refocus on one of the ways to recycle water—through the reuse of urban wastewater, for irrigation and other purposes. This could release clean water for use in other sectors that need fresh water and provide water to sectors that can utilize wastewater e.g., for irrigation and other ecosystem services. In general, wastewater comprises liquid wastes generated by households, industry, commercial sources, as a result of daily usage, production, and consumption activities. Municipal treatment facilities are designed to treat raw wastewater to produce a liquid effluent of suitable quality that can be disposed to the natural surface waters with minimum impact on human health or the environment. The disposal of wastewater is a major problem faced by municipalities, particularly in the case of large metropolitan areas, with limited space for land[1]based treatment and disposal. On the other hand, wastewater is also a resource that can be applied for productive uses since wastewater contains nutrients that have the potential for use in agriculture, aquaculture, and other activities. In both developed and developing countries, the most prevalent practice is the application of municipal wastewater (both treated and untreated) to land. In developed countries where environmental standards are applied, much of the wastewater is treated prior to use for irrigation of fodder, fiber, and seed crops and, to a limited extent, for the irrigation of orchards, vineyards, and other crops. Other important uses of wastewater include, recharge of groundwater, landscaping (golf courses, freeways, playgrounds, schoolyards, and parks), industry, construction, dust control, wildlife habitat improvement and aquaculture. In developing countries, though standards are set, these are not always strictly adhered to. Wastewater, in its untreated form, is widely used for agriculture and aquaculture and has been the practice for centuries in countries such as China, India and Mexico. Thus, wastewater can be considered as both a resource and a problem. Wastewater and its nutrient content can be used extensively for irrigation and other ecosystem services. Its reuse can deliver positive benefits to the farming community, society, and municipalities. However, wastewater reuse also exacts negative externality effects on humans and ecological systems, which need to be identified and assessed. Before one can endorse wastewater irrigation as a means of increasing water supply for agriculture, a thorough analysis must be undertaken from an economic perspective as well. In this regard the comprehensive costs and benefits of such wastewater reuse should be evaluated. Conventional cost benefit analysis quite often fails to quantify and monetize externalities associated with wastewater reuse. Hence, environmental valuation techniques and other related tools should be employed to guide decision-making. Moreover, the economic effects of wastewater irrigation need to be evaluated not only from the social, economic, and ecological standpoint, but also from the sustainable development perspective. Pakistan is a case which illustrates this problem. Both treated and untreated municipal wastewater in the vicinity of large cities like Faisalabad is used for vegetable production. But, how safe is this practice? How does one tradeoff between the obvious benefits of this use and the costs associated with it?

Soil hydrology determines the water–soil–plant interactions in the Earth’s system because porous medium acts as an interface within the atmosphere and lithosphere; regulates main processes such as runoff discharge, aquifer recharge, movement of water, and solutes into the soil; and ultimately the amount of water retained and available for plants growth. Soil hydrology can be strongly affected by land management. Therefore, investigations aimed at assessing the impact of land management changes on soil hydrology are necessary, especially to optimize water resources. This Special Issue collects 12 original contributions addressing the state-of-the-art advances in soil hydrology for sustainable land management. These contributions cover a wide range of topics including (i) the effects of land use change, (ii) water use efficiency, (iii) erosion risk, (iv) solute transport, and (v) new methods and devices for improved characterization of soil physical and hydraulic properties. They include both field and laboratory experiments as well as modelling studies. Different spatial scales, i.e., from field to regional scales, and a wide range of geographic regions are also covered. The collection of these manuscripts presented in this Special Issue provides a relevant knowledge contribution for effective saving water resources and sustainable land management.

Introduction: The following Standards for Landscape Irrigation Systems replace the previous publication of March 1997. They have been developed by the Irrigation Industry Association of British Columbia to reflect the current minimum Standards for the industry and to provide guidance to its members as a benchmark for their performance. The principles embodied in these Standards apply to all landscape irrigation systems but the special circumstances of some owners or installations may require the development of more customized specifications related to the project. The use of these Standards is intended to encourage efficient and responsible water management and result in irrigation systems that are economical, practical, and sustainable. Owners, designers, and installers of these systems are responsible for the use of a precious and finite resource to maintain healthy and functional landscapes. Accepted industry practice reflects these goals. The Irrigation Industry Association of British Columbia accepts no liability arising from the use of these Standards in contractual relationships between parties to an irrigation project.