Water Use Growth Research Articles

Rising vegetation activity dominates growing water use efficiency in the Asian permafrost region from 1900 to 2100

Permafrost play an important role in regulating global climate system. We analyzed the gross primary productivity (GPP), net primary productivity (NPP), and evapotranspiration (ET) derived from MODIS and three earth system models participated in the Coupled Model Inter-comparison Project Phase 6 (CMIP6) in the Asian permafrost region. The water use efficiency (WUE) was further computed. The simulated GPP, NPP, and ET show slightly increasing trends during historical period (1900–2014) and strong increasing trends in projection period (2015–2100), and projected impacts of climate change on all variables are greater under high-emission scenarios than low-emission scenarios. Further analysis revealed higher increases in GPP and NPP than that of ET, indicating that vegetation carbon sequestration governs the growing WUE under historical and projected periods in this region. The GPP, NPP and ET showed higher changing rates in western, central and southeast areas of this region, and WUE (WUEGPP, and WUENPP) shows the similar spatial pattern. Compared to MODIS-derived GPP, NPP, and ET during 2000–2014, Earth system models yield the best estimates for NPP, while slight underestimations for GPP and ET, and thus slight overestimations for WUEGPP and WUENPP. This study highlights the predominant role of vegetation activity in regulating regional WUE in Asian permafrost region under future climate change. Vegetation domination of the growing water use efficiency implies that the permafrost region may continue acting efficiently in sequestrating atmospheric carbon in terms of water consumption throughout the 21st century.

Assessing Water Resource Issues Among States in the US South East Region

The US Southeast region is endowed with vast deposits of water resource assets located in numerous states. Considering the growing water use to serve rapidly expanding land uses from agriculture, residential areas, thermoelectric to industrial facilities. Over the years, the demand for water to meet the needs of various sectors in the zone has precipitated increased withdrawals, declining levels in aquifers and sectorial imbalance in the distribution. Accordingly, sectorial imbalance and stress attributed to socio-economic, physical and ecological parameters is now being felt in the areas many considered fully endowed with hydrological assets and less vulnerable to depletion. Beset by the management implications of the trends, various agencies in the zone have stepped up mitigation measures. Notwithstanding the gravity of the challenges and the fact that most studies are still festooned with projected depletion patterns in the US arid West, very little work exists in the literature on the changing patterns in water resource use in the Southeast region using a mix scale model. For that, this research will fill that void by assessing the variabilities in water resource use among some states in the Southeast. With emphasis on the issues, trends, factors, and impacts, the study uses secondary info from major data agencies analyzed by mix scale techniques of descriptive statistics and Geographic Information Systems (GIS) to assess the tendencies. The results point to changes in usage among the sectors in the form of gains and declines, the emergence of hydroelectricity and irrigation as the largest users, the dominance of Florida, regional dependence on surface water sources, evidence of depletion and spatial dispersion of these trends across the states. With these changes attributed to various elements, the paper offered suggestions ranging from water conservation measures, the adoption of efficient polices to the design of a regional hydrological information system.

Effects of water management and cultivar on carbon dynamics, plant productivity and biomass allocation in European rice systems

Water saving techniques, such as alternate wetting and drying (AWD), are becoming a necessity in modern rice farming because of climate change mitigation and growing water use scarcity. Reducing water can vastly reduce methane (CH4) emissions; however, this net climate benefit may be offset by enhanced carbon dioxide (CO2) emissions from soil. The main aims of this study were: to determine the effects of AWD on yield and ecosystem C dynamics, and to establish the underlying mechanistic basis for observed trends in net ecosystem C gain or loss in an Italian rice paddy. We investigated the effects of conventional water management (i.e. conventionally flooded paddy; CF) and AWD on biomass accumulation (aboveground, belowground, grain), key ecosystem C fluxes (net ecosystem exchange (NEE), net primary productivity (NPP), gross primary productivity (GPP), ecosystem respiration (ER), autotrophic respiration (RA), heterotrophic respiration (RH)), and soil organic matter (SOM) decay for four common commercial European rice cultivars. The most significant finding was that neither treatment nor cultivar affected NEE, GPP, ER or SOM decomposition. RA was the dominant contributor to ER for both CF and AWD treatments. Cultivar and treatment affected the total biomass of the rice plants; specifically, with greater root production in CF compared to AWD. Importantly, there was no effect of treatment on the overall yield for any cultivar. Possibly, the wetting-drying cycles may have been insufficient to allow substantial soil C metabolism or there was a lack of labile substrate in the soil. These results imply that AWD systems may not be at risk of enhancing soil C loss, making it a viable solution for climate change mitigation and water conservation. Although more studies are needed, the initial outlook for AWD in Europe is positive; with no net loss of soil C from SOM decomposition, whilst also maintaining yield.

Applying the Water Footprint and dynamic Structural Decomposition Analysis on the growing water use in China during 1997–2007

China has experienced rapid economic development during the recent years. In the meantime, the total water use in China has greatly increased, causing considerably severe water shortage. To quantify how the social-economic development drives the change of water use is of great importance for Chinese government. This study aims to quantitatively investigate the determinants of the growing water use in China during 1997–2007. China's water usages in 1997–2007 are indicated by the Internal Water Footprint (IWF), External Water Footprint (EWF), and Exported Virtual Water (ExVW) using an input–output based WF analysis. A dynamic Structural Decomposition Analysis (SDA) model is employed to decompose the changes in the total WFs (TWF) into five social-economic determinants. The dynamic SDA model, which uses a nonlinear path function to simulate the real paths followed by determinants, is a further development of a path-based SDA algorithm. To validate the dynamic SDA, a comparison study is carried out against the commonly used mean decomposition model. The results from the WF analysis show that, during 1997–2007, the increase of China's water use is dominated by the ExVW, which increases significantly due to the expansion of exports. While the changes in the IWF and EWF tend to help mitigating the water pressure. The dynamic decomposition results indicate that the consumption level is the dominant factor of China's water use growth, and the changes in water-saving technology and final demand pattern contribute largely to offsetting the water use growth. The model comparison shows that the dynamic SDA model is more advanced in obtaining reliable results and addressing the static issue of traditional SDA models. This study provides a robust framework for understanding the water use situation from the social-economic perspectives, which benefits sustainable water management.

Integrated Water Resource Management and Water Sharing

Integrated water resource management (IWRM) and water sharing concepts are described. Various definitions of IWRM are presented. It can be described as a facilitated stakeholder process to promote coordinated activities in pursuit of common goals for multiple objective development and management of water founded in sustainable water resource systems. Sustainable water resource systems support social objectives into the indefinite future without undermining hydrologic and ecological integrity. IWRM is comprised of objectives, institutions, implementation, and adaptation, reflecting merging of top-down and bottom-up approaches. It can assume many institutional forms, and is best implemented at the river basin or subbasin scales. Several water sharing models and principles are introduced. Examples of mature yet different IWRM governance structures in California and France are presented. Wide-scale adoption of IWRM remains elusive. Changing societal values, increasing water demands, growing water use conflicts, and link to poverty reduction and economic development provide impetus to adopt IWRM; it remains a promising mechanism to better use and share water to balance economic, environmental, and social aspects that underpin sustainable development.