Advances in multi-stage planning and implementing managed aquifer recharge for integrated water management

Managed aquifer recharge (MAR) is the umbrella term for a range of technologies that enable the integrated use and management of surface water and groundwater to achieve a wide and growing range of social, economic and environmental benefits. The extent and variety of its applications and benefits have mushroomed in recent years as demonstrated in the suite of papers contained within this Special Issue of Sustainable Water Resources Management. This paper introduces the Special Issue and draws together some insights arising from the findings of these papers. Managed aquifer recharge projects normally evolve through a development cycle that covers planning, investigations, pilot scale trials and then implementation of full-scale projects. This Special Issue starts with four papers that synthesize information from a large number of MAR sites, to demonstrate the scope and geographic distribution of international efforts in MAR, factors affecting the economics of MAR projects, and efforts to find metrics to compare their performance among sites and over time. Then there are four papers describing some significant and widely contrasting completed MAR projects in four continents covering their development, what has been learned and some operational issues. Given this context, the next five papers explore the implementation and evaluation of pilot projects in three countries. These papers address issues ranging from hydrogeological characterization, evaluating impacts on groundwater-dependent ecosystems to community participation. All papers to this point give context to the final five papers that show the planning and preliminary studies performed to select MAR sites, to design pilot projects or to explore the feasibility of large-scale MAR programs. Arranging the sequence of papers in this way is intended to yield an understanding of the need for the investigations and modelling to produce viable projects, and to help readers to consider some important practical questions. What steps are needed for any given project to: define objectives; build partnerships; engage with communities; assemble evidence of technical viability, sustainability and safety; secure funding; design and construct efficiently; streamline operations; and finally to monitor the extent to which a completed project met its goals? These papers were developed out of a broader selection of papers presented at the 9th International Symposium on Managed Aquifer Recharge (ISMAR9), Mexico City, June 2016. They are a companion to another Special Issue arising from ISMAR9, published in the journal Water on the complementary theme "Water Quality Considerations for Managed Aquifer Recharge Systems" edited by Prof. Dr. Pieter Stuyfzand and Dr. Niels Hartog (2017). These Issues are a contribution of the International Association of Hydrogeologists Commission on Managing Aquifer Recharge (IAH-MAR) to the advancement and dissemination of knowledge for wise application of MAR.