This planetary boundaries framework update finds that six of the nine boundaries are transgressed, suggesting that Earth is now well outside of the safe operating space for humanity. Ocean ...acidification is close to being breached, while aerosol loading regionally exceeds the boundary. Stratospheric ozone levels have slightly recovered. The transgression level has increased for all boundaries earlier identified as overstepped. As primary production drives Earth system biosphere functions, human appropriation of net primary production is proposed as a control variable for functional biosphere integrity. This boundary is also transgressed. Earth system modeling of different levels of the transgression of the climate and land system change boundaries illustrates that these anthropogenic impacts on Earth system must be considered in a systemic context.
Transgression of planetary boundaries by human activities have now brought humanity well beyond a “safe operating space.”
Increasing groundwater contamination across the globe triggered the concept of “aquifer vulnerability”, which has been extensively used worldwide during past three to four decades by researchers and ...policy makers for protecting groundwater from pollution. However, only a few recent studies have focused on the performance evaluation of two or more vulnerability assessment methods. Some of these studies have resulted in contrasting findings. Given this fact and considering growing threat of groundwater contamination due to increasing human activities across the globe, it is necessary to critically review existing methods, understand current research trends, and identify major challenges associated with the assessment of aquifer vulnerability. Hence, the aim of this study is to present a comprehensive review of the methods and approaches used for the evaluation of aquifer vulnerability for ‘resource’ and ‘source’ protection. First, the concept and types of aquifer vulnerability along with the definitions evolved over the years are presented, and then the methods for assessing aquifer vulnerability are suitably classified and briefly discussed. Second, the concept of vulnerability assessment for ‘source’ protection is highlighted, and the evolution of groundwater vulnerability evaluation methods is presented with an enlightening block diagram. Third, current research trends and critiques on past studies are discussed. Fourth, the major challenges of vulnerability assessment are highlighted and a way forward is suggested. It is concluded that the progress of vulnerability evaluation methods has not kept pace with the advancement of knowledge and tools/techniques. There is an urgent need for developing a scientifically robust and somewhat versatile methodology for the evaluation of ‘intrinsic’ and ‘specific’ groundwater vulnerability for ‘resource’ and ‘source’ protection under varying hydrogeologic and hydro-climatic conditions. It is emphasized that more studies should be devoted to vulnerability assessment for ‘source’ protection using ‘Source-Pathway-Receptor/Target’ approach. Also, spatial decision support systems should be developed using modern tools/techniques including artificial intelligence to improve decision-making process for protecting vital groundwater resources.
•This study presents a review of methods used for mapping of groundwater vulnerability to pollution.•Methods widely used for assessing aquifer vulnerability are classified into suitable groups and their overview is provided.•We illustrated evolution of groundwater vulnerability methods by an enlightening block diagram, and methods are critiqued.•Future challenges are identified and a way forward is suggested.•This study emphasizes need of a robust and versatile method using modern tools for groundwater vulnerability evaluation.
•Impacts of cultivation practices on the infiltration process of lateritic soils are investigated.•Infiltration models are assessed for simulating infiltration behavior at plot and field ...scales.•Swartzendruber model gives best estimates of saturated hydraulic conductivity.•Swartzendruber, Brutsaert and Kostiakov-Lewis models show best fitting ability.•Infiltration characteristics of lateritic soils are greatly affected by cultivation practices.
Lateritic vadose zone, mostly found in tropical humid regions, is very complex and hence behaves in a different way than other vadose zones. Until now, little is known about the impact of agricultural practices on the infiltration dynamics of such vadose zones. To this end, the present study was conceived to explore infiltration characteristics of lateritic soil-water zones by conducting 72 double-ring infiltration experiments at multiple sites considering both plot and field scales having paddy-wheat cultivation practices. Furthermore, five infiltration models, two empirical (Kostiakov and Kostiakov-Lewis) and three process-based (Philip Two-Term, Swartzendruber and Brutsaert) were fitted to the site-specific infiltration data and their performance was critically evaluated for modeling infiltration behavior of the lateritic vadose zone. Results indicated that the mean ‘quasi-steady infiltration rate’ of the Experimental Plot measured before paddy cultivation was about 0.23 ± 0.2 mm/min, which decreased by around 80% after paddy cultivation and then increases by more than 200% after wheat cultivation. Similarly, at the field scale, the ‘quasi-steady infiltration rate’ decreases by about 60% after paddy cultivation. The Swartzendruber model followed by the Brutsaert model provided the most reliable estimates of saturated hydraulic conductivity. The Swartzendruber, Brutsaert and Kostiakov-Lewis models showed a greater fitting ability in predicting ‘cumulative infiltration’ under all cultivation practices at both plot and field scales. In contrast, all the five infiltration models predicted infiltration rate with a lower accuracy than the cumulative infiltration. It is concluded that the infiltration characteristics of lateritic vadose zones are greatly influenced by cultivation practices as well as by macro-pores and low-permeability layers present in the soil profile. Given the significant field heterogeneity, future studies should explore the efficacy of other process-based infiltration models e.g., the Smith and Parlange (1978) model, the Kutílek and Krejča model (1987), and the modified Green-Ampt models in predicting the infiltration characteristics of lateritic terrains.
•GRACE data and GRACE-derived products have greatly underutilized potential for sustainable groundwater management.•Divergent opinions from researchers and practitioners are collected regarding the ...use of GRACE as a tool for groundwater management.•Mismatch between science supply and users’ demand indicates the need for effective communication and mutual understanding.
Managing groundwater is challenging because its below-ground existence makes the resource difficult to monitor. GRACE is an important tool as it provides the opportunity to monitor the storage of groundwater. While GRACE-based groundwater studies have focused on many regions across the globe, studies that link scientific research to policymaking and groundwater practices are still limited. This paper aims to provide recommendations for the improved use of GRACE data for the purpose of sustainable groundwater management. To gain insight into this, a policy Delphi survey was conducted to collect opinions from both the academic and non-academic communities. Although opinions are divergent and a mismatch exists between what science (researchers) currently supplies and what users (practitioners) demand, we found that both communities acknowledged the potential of GRACE data and GRACE-derived products for groundwater management and would be willing to collaborate to develop projects for practical applications. Better communication between researchers and practitioners was recommended as key for greater application of GRACE-derived products into practice. Practitioners noted the need for reliable data for management responsibilities but prefer locally-observed data. The reliability of GRACE at local scales was raised by practitioners as a limitation despite advances in downscaling methods within the academic community. The survey reveals a shared desire for more comparison between GRACE-derived products with local measurements to determine whether GRACE products can be useful for informing local decisions. Using survey outcomes, we propose three recommendations to improve the usefulness of GRACE-derived and other remote sensing products for groundwater management and practices: improving communication strategies; increasing data accuracy, transparency and accessibility to build trust; and conducting solution-oriented research.
Increasing recognition of the importance of ecosystem services in water resources management has accelerated the development and application of environmental‐flows requirements for lotic ecosystems. ...However, most environmental‐flows management focuses on water infrastructure, such as dams or diversions, without explicitly taking groundwater into account and ignoring the importance of groundwater environmental flow contribution. In this study two methods for estimating groundwater environmental flow contributions are presented: (a) a groundwater‐centric method (based on the Sustainability Boundary Approach), which proposes that high levels of ecological protection are maintained if 90% of groundwater discharge is preserved, and (b) a surface water‐centric method (novel method), which quantifies groundwater environmental flow contributions from streamflow using region‐specific streamflow sensitivity metrics and local environmental‐flows policies. The two methods were tested in British Columbia, Canada, which has a diverse, complex, and highly coupled groundwater‐surface water system. The two methods gave comparable results in various hydro‐geoclimatic settings. Although British Columbia was used as a case study, this framework can be implemented across various spatial and temporal scales for different regions and globally, in data‐scarce, hydrologically complex landscapes. Application of these methods can aid in a robust and holistic assessment of environmental‐flows, taking into account the often‐missing groundwater component.
Plain Language Summary
Growing recognition of the importance of ecosystem services to the development and management of water resources has spurred the development and application of environmental‐flows requirements. Despite the importance of groundwater in maintaining the freshwater ecosystem, groundwater is seldom taken into consideration in environmental‐flows allocation and management. This study presents two methods for estimating groundwater environmental flow contributions: (a) a groundwater‐centric method (based on the Sustainability Boundary Approach), and (b) a surface water‐centric method (novel method). The two methods are demonstrated, using the Canadian westernmost province of British Columbia as a case study. The framework presented in this study can be implemented across different spatial and temporal scales for different regions and globally, in data‐scarce, hydrologically complex landscapes. Application of these methods can aid in a robust and holistic assessment of environmental‐flows, taking into account the often‐missing groundwater component.
Key Points
A novel surface water‐centric method for estimating groundwater environmental flow contributions is developed and demonstrated
Results from two methods were in agreement at regional, biogeoclimatic and hydrozone scales in a hydrologically diverse study area
With currently used input resolution, the methods were particularly useful in mapping overall patterns of groundwater contributions to environmental flow
Due to poor water resources management, groundwater-dependent agriculture induces substantial stress on several aquifer systems worldwide, which poses a serious threat to water and food security. ...However, only a few studies have addressed this vital issue. This study aimed to evaluate stress on aquifers due to the overuse of groundwater for food production and explore pathways for stress reduction via improved irrigation efficiency and productivity. Groundwater stress was characterized using the ratio of water use to availability, with consideration for environmental flows. The results indicated that out of 107 countries—dependent on groundwater irrigation, about half are overexploiting groundwater, while one-fifth of these countries are extracting moderately-to heavily. Over 90% of the non-renewable groundwater abstraction occurs in 7 countries. Further, about 450 million tonnes (Mt) of global annual food production is from non-renewable groundwater exploitation. If the existing irrigation efficiency is increased to 90%, current groundwater stress would be reduced by 40%. Additionally, in unstressed regions, it would be possible to produce additional 300 Mt of food by using saved water while maintaining groundwater stress at acceptable levels. Moreover, improved water productivity in conjunction with increased irrigation efficiency could reduce the current level of unsustainable food production by 47%. These results provide important insights into the dynamics of irrigation stress on groundwater systems, and the role of managerial interventions.
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