Abstract: Humans have relied on agriculture to feed their communities for thousands of years. Irrigation is practiced in many different forms over the years in countries all over the world. Although modern irrigation systems have been developed, and are in use in many countries, ancient irrigation systems (AISs) have also played a major role in sustaining food production, especially in smallholder farming in least developed and developing countries. The editorial team of Agricultural Systems put out a call for a special issue on restoring AISs for sustainable agro-ecosystems development to capture ancient marvels of traditional irrigation technology across the world. The objectives of this special issue were to: (i) understand and analyse the hydrological and socio-economic networks anchored by AISs; (ii) explain the nature and sustainability of management of these systems in relation to local agro-ecosystems; (iii) analyse the implications of the AISs for land, soil and water quality, and agro-ecosystem services; (iv) qualitative and quantitative analysis of AISs, including bio-physical and bio-economic modelling of these systems; and (v) assess the feasibility of alternative technological, institutional and management strategies to enhance the productivity, profitability, and environmental sustainability of the systems. The overall goal of the special issue was to develop a useful repository for this information as well as to use the journal’s international reach to share this information with the agricultural systems research community and journal readership. This paper provides reflections of papers published in the special issue. The special issue resulted in twelve high quality original research articles and one review article from Asia, Africa and Europe. The findings from various papers revealed that the AISs have been degraded due to human interventions or the anthropogenic activities across the world. Various papers emphasized that as a corrective measure, there is a need for developing and implementing rehabilitation projects in these systems. Authors identified that appropriate policy interventions by the relevant authorities would be a major step towards such rehabilitation process. However, resetting the ecosystem structure of the AISs strictly towards their historical manifestation is neither required nor feasible in the present context as it would contradict the expectations of stakeholders from these systems. The knowledge generated through the special issue provides evidence-based information on various aspects of AISs. It helps aware governments, private sectors and development agencies for improved policy planning and decision making and for prioritizing the restoration, rehabilitation, and management of various AISs around the world.

Abstract: Combined large-scale rainwater harvesting (RWH) and flood mitigation systems are promising as a sustainable water management strategy in urban areas. These are multi-purpose infrastructure that not only provide a secondary, localised water resource, but can also reduce discharge and hence loads on any downstream wastewater networks if these are integrated into the wider water network. However, the performance of these systems is dependent on the specific design used for its local catchment which can vary significantly between different implementations. A multitude of design strategies exist, however there is no universally accepted standard framework. To tackle these issues, this paper presents a two-player optimisation framework which utilises a stochastic design optimisation model and a competing, high-intensity rainfall design model to optimise passively-operated RWH systems. A customisable tool set is provided, under which optimisation models specific to a given catchment can be built quickly. This reduces the barriers to implementing computationally complex sizing strategies and encouraging more resource-efficient systems to be built. The framework was applied to a densely populated high-rise residential estate, eliminating overflow events from historical rainfall. The optimised configuration resulted in a 32% increase in harvested water yield, but its ability to meet irrigation demands was limited by the operational levels of the treatment pump. Hence, with the inclusion of operational levels in the optimisation model, the framework can provide an efficient large-scale RWH system that is capable of simultaneously meeting water demands and reducing stresses within and beyond its local catchment.

Abstract: More than 4,000 sandstone-hosted uranium occurrences host over 1.2 billion pounds of mined and in situ U3O8 throughout the Colorado Plateau. Most of the resources are in two distinct mineral systems with deposits hosted in the Triassic Chinle and Jurassic Morrison Formations. In the Chinle mineral system, base metal sulfides typically accompany mineralization. The Morrison mineral system is characterized by V/U ratios up to 20. The uranium source was likely volcanic ash preserved as bentonitic mudstones in the Brushy Basin Member of the Morrison Formation, and lithic volcanic clasts, ash shards, and bentonitic clay in the lower part of the Chinle Formation. Vanadium originated from two possible sources: iron–titanium oxides that are extensively altered in bleached rock near deposits or from similar minerals in variably bleached red beds interbedded with and beneath the Morrison. In Chinle-hosted deposits, in addition to volcanic ash, a contributing source of both vanadium and uranium is proposed here for the first time to be underlying red beds in the Moenkopi and Cutler Formations that have undergone a cycle of reddening-bleaching-reoxidation. Transport in both systems was likely in groundwater through the more permeable sandstones and conglomerate units. The association of uranium minerals with carbonate and more rarely apatite, suggests that transport of uranium was as a carbonate or phosphate complex. The first comprehensive examination of paleoclimate, paleotopography, and subsurface structure of aquifers coupled with analysis of the geochronology of deposits suggests that that there were distinct pulses of uranium mineralization/redistribution during the period from about 259 Ma to 12 Ma when oxidized mineralizing fluids were intermittently rejuvenated in the Plateau in response to changes in tectonic regime and climate. Multiple lines of evidence indicate that deposits formed at ambient temperatures of about 25 °C to no greater than about 140 °C. In both systems, deposits formed where groundwater flow slowed and was subject to evaporative concentration. Stagnant conditions allowed for prolonged interaction of U- and V-enriched groundwater with ferrous iron-bearing reductants, such as illite and iron–titanium oxides, and more rarely organic material such as plant debris. Paragenetically late in the sequence, reducing fluids introduced additional organic matter to some deposits. Reducing fluids and introduced organic matter (now amorphous and altered by radiolysis) may originate from regional petroleum systems where peak oil and gas generation was from ∼ 82 to ∼ 5 Ma. Our novel analysis indicates that these reducing fluids bleached rock and protected affected deposits from remobilization during exposure and weathering that followed uplift of the Plateau (∼80 to 40 Ma).