Some Characteristics and Impacts of the Drought and Water Crisis in Southeastern Brazil during 2014 and 2015

Since the austral summer of 2014 southeastern Brazil has been experiencing one of the most severe droughts in decades. This rainfall deficiency has generated water shortages and a water crisis that have affected population and local economies in the metropolitan region of Sao Paulo, the largest megacity in South America. By January 2015, main reservoirs had reached storage levels of only 5% of their 1.3 billion m3 capacity. The meteorological causes of the drought situation were linked to changes in the regional circulation, characterized by a mid-troposphere blocking high that lasted 45 days during the summer of 2014 over southeastern Brazil, something not seen in five decades. The water crisis was aggravated by a combination of lack of rainfall and higher temperatures, the summer of 2014 being the warmest and driest over the Cantareira reservoir system since 1951. Increasing population and water consumption increased vulnerability in the region, and while human-induced warming may not have generated the atmospheric conditions behind the 2014 and 2015 summer droughts in Southeast Brazil, it is more likely that the warm temperatures have affected the severity of the drought and exacerbated the impacts on the population.

Preventing a Water Crisis

Water security in Africa has never been as starkly highlighted as the countdown to Day Zero in Cape Town. South Africa, where becauseof an unprecedented drought, the entire city of about 4 million residents could be without water in July. Water restrictions for all residents are already in place and Day Zero has an activation date of July 9 （at the time of writing）. If this catastrophe happens, it would make the famous tourist city that is frequently voted the world＇s most beautiful destination, earn another more dubious title that of the first major city in the world to ever run out of water.

Crisis of Water Resources on the Ulan Buh Desert Oases, Inner Mongolia, China-A Case Study of Dengkou County

Hetao Plain, composed of hundreds of oases, is one of the most important grain-producing areas in China. Most crops, especially wheat and corn, depend on irrigation, thus water availability is a key issue for grain productivity on this land. The Yellow River is the main water source for irrigation and a crisis of water resources for agricultural use occurs because of increasingly reduced river flows and water-using competition with industry and human residential use. In order to understand the current situation and distribution of water resources on these oases, we collected 20-yr＇s data of river runoff, irrigation volumes, infiltration and precipitation to examine the relationships between water resources distribution and its agricultural use. We found that the oasis in Dengkou county was short of water resources with a water deficit rate of 5.14% in 2010. Based on the trend of the data, water deficit will continue to increase as the population grows in the future. Water resource is a limiting factor to agricultural development in this region and proper management of water use and strategies for water resource conservation are urgently needed. Especially, based on our results we suggest that current irrigation methods need to be greatly improved to save the water that was lost from evaporation.

An overview of reclaimed water reuse in China

China is facing severe water problems including scarcity and pollution which are now becoming key factors restricting developments. Creating an alternative water resource and reducing effluent discharges, water reuse has been recognized as an integral part of water and wastewater management scheme in China. The government has launched nationwide efforts to optimize the benefits of utilizing reclaimed water. This article reviewed the water reuse activities in China, including： （1） application history and current status; （2） potentials of reclaimed water reuse; （3） laws, policies and regulations governing reclaimed water reuse; （4） risks associated with reclaimed water reuse; （5） issues in reclaimed water reuse. Reclaimed water in Beijing and Tianjin were given as examples. Suggestions for improving the efficiencies of reusing urban wastewater were advanced. Being the largest user of reclaimed wastewater in the world, China＇s experience can benefit the development of water reuse in other regions.

Watershed science:Linking hydrological science with sustainable management of river basins

Over the past decades,a number of water sciences and management programs have been developed to better understand and manage the water cycles at multiple temporal and spatial scales for various purposes,such as ecohydrology,global hydrology,sociohydrology,supply management,demand management,and integrated water resources management(IWRM).At the same time,rapid advancements have also been taking place in tracing,mapping,remote sensing,machine learning,and modelling technologies in hydrological research.Despite those programs and advancements,a water crisis is intensifying globally.The missing link is effective interactions between the hydrological research and water resource management to support implementation of the UN Sustainable Development Goals(SDGs)at multiple spatial scales.Since the watershed is the natural unit for water resources management,watershed science offers the potential to bridge this missing link.This study first reviews the advances in hydrological research and water resources management,and then discusses issues and challenges facing the global water community.Subsequently,it describes the core components of watershed science:(1)hydrological analysis;(2)water-operation policies;(3)governance;(4)management and feedback.The framework takes into account water availability,water uses,and water quality;explicitly focuses on the storage,fluxes,and quality of the hydrological cycle;defines appropriate local water resource thresholds through incorporating the planetary boundary framework;and identifies specific actionable measures for water resources management.It provides a complementary approach to the existing water management programs in addressing the current global water crisis and achieving the UN SDGs.

Upgrading to urban water system 3.0 through sponge city construction

Facing the pressure of excessive water consumption, high pollution load and rainstorm waterlogging,linear and centralized urban water system, system 2.0, as well as traditional governance measures gradually exposed characters of water-sensitivity, vulnerability and unsustainability, subsequently resulting in a full-blown crisis of water shortage, water pollution and waterlogging. To systematically relieve such crisis, we established urban water system 3.0, in which decentralized sewerage systems, sponge infrastructures and ecological rivers play critical roles. Through unconventional water resource recycling, whole process control of pollutions and ecological restoration, system 3.0 with integrated management measures, is expected to fit for multiple purposes which involve environmental,ecological, economic and social benefits. With advantages of flexibility, resilience and sustainability, water system 3.0 will show an increasingly powerful vitality in the near future.

Bio-inspired Fog Harvesting Materials:Basic Research and Bionic Potential Applications

With the explosive growth of the world's population and the rapid increase in industrial water consumption,the world's water supply has fallen into crisis.The shortage of fresh water resources has become a global problem,especially in arid regions.In nature,many organisms can collect water from foggy water under harsh conditions,which provides us with inspiration for the development of new functional fog harvesting materials.A large number of bionic special wettable synthetic surfaces are synthesized for water mist collection.In this review,we introduce some water collection phenomena in nature,outline the basic theories of biological water harvesting,and summarize six mechanisms of biological water collection:increased surface wettability,increased water transmission area,long-distance water delivery,water accumulation and storage,condensation promotion,and gravity-driven.Then,the water collection mechanisms of three typical organisms and their synthesis are discussed.And their function,water collection efficiency,new developments in their biomimetic materials are narrated,which are cactus,spider and desert beetles.The study of multiple bionics was inspired by the discovery of Nepenthes,moist and smooth peristome.The excellent characteristics of a variety of biological water collection structures,combined with each other,are far superior to other single synthetic surfaces.Furthermore,the main problems in the preparation and application of biomimetic fog harvesting materials and the future development trend of materials fog harvesting are prospected.

Off-flavor compounds from decaying cyanobacterial blooms of Lake Taihu

The effect of cyanobacterial bloom decay on water quality and the complete degradation of cyanobacterial blooms in a short period were examined by an enclosure experiment in Gonghu Bay of Lake Taihu,China.Water quality parameters as well as taste and odor compounds during the breakdown of cyanobacterial blooms were measured.Results showed that the decay of cyanobacterial blooms caused anoxic water conditions,decreased pH,and increased nutrient loading to the lake water.The highest concentrations of dimethyl sulfide （DMS）,dimethyl trisulfide （DMTS）,and β-cyclocitral were observed in the anoxic water,at 62331.8,12413.3,and 1374.9 ng/L,respectively.2-Methylisoborneol was dominant during the live growth phase of cyanobacterial blooms,whereas DMS and DMTS were dominant during the decomposition phase.Dissolved oxygen,pH,and chlorophyll a were negatively correlated with DMS,DMTS,and β-cyclocitral,whereas total phosphorus,total nitrogen,and ammonium （NH4＋-N） were positively correlated with DMS,DMTS,β-cyclocitral,and β-ionone.The experimental results suggested that preventing the anaerobic decomposition of cyanobacterial blooms is an important strategy against the recurrence of a malodor crisis in Lake Taihu.