Water resources management (WRM) for sustainable development presents many challenges in areas with sparse in situ monitoring networks. The exponential growth of satellite based information over the ...past decade provides unprecedented opportunities to support and improve WRM. Furthermore, traditional barriers to the access and usage of satellite data are lowering as technological innovations provide opportunities to manage and deliver this wealth of information to a wider audience. We review data needs for WRM and the role that satellite remote sensing can play to fill gaps and enhance WRM, focusing on the Latin American and Caribbean as an example of a region with potential to further develop its resources and mitigate the impacts of hydrological hazards. We review the state‐of‐the‐art for relevant variables, current satellite missions, and products, how they are being used currently by national agencies across the Latin American and Caribbean region, and the challenges to improving their utility. We discuss the potential of recently launched, upcoming, and proposed missions that are likely to further enhance and transform assessment and monitoring of water resources. Ongoing challenges of accuracy, sampling, and continuity still need to be addressed, and further challenges related to the massive amounts of new data need to be overcome to best leverage the utility of satellite based information for improving WRM.
Key Points
Satellite remote sensing is being incorporated into water resources management but is generally underutilized
New and proposed missions have the potential to transform water resources management for sustainable development, especially in data‐poor regions
Ongoing challenges of accuracy, sampling, and continuity and capacity development need to be addressed, as well as new challenges of information volume and diversity
Determination of the field‐saturated hydraulic conductivity (Kfs) can result in very high variability due to soil heterogeneity, the measurement method, the number of replications, and the Kfs ...calculation method used. Especially for dryland soils, stoniness can influence infiltration rates significantly. To identify this variability as well as its source, six widely used measurement methods were compared: single‐ring (SR) and double‐ring (DR) infiltrometers, the constant‐head well infiltrometer (CH), the inverse auger hole method (IA), the tension infiltrometer (TI), and the rainfall simulator (RFS). The six methods were applied at three locations in a semiarid part of Chile that showed moderate (15%) to high (55%) stoniness. Additionally, Kfs variations due to different calculation techniques for the same measurement method were thoroughly investigated. Results showed that different calculation techniques sometimes gave significantly different estimates of Kfs when using the same data set, and those relative differences were conserved among measurement locations. The borehole methods (IA and CH) showed high discard rates due to stoniness, making these methods less appropriate. The SR and DR methods gave considerably higher Kfs estimates, while the RFS and TI proved good candidates as reference methods for stony soils, with low failure rates and coefficients of variation.
Regional frequency analysis based on L-moments was applied to assess the spatial extent of meteorological droughts in tandem with their return periods in Zambia. Weather station monthly rainfall data ...were screened to form homogeneous sub-regions-, validated by a homogeneity criterion and fitted by a generalized extreme value distribution using goodness-of-fit test statistics. Predictor equations at regional scale for L-moment ratios and mean annual precipitation were developed to generate spatial maps of meteorological drought recurrences. The 80% of normal rainfall level and two thresholds of 60% and 70% were synonymous with moderate and severe droughts, respectively. Droughts were more severe in the south than in the north of Zambia. The return periods for severe and moderate droughts showed an overlapping pattern in their occurrence at many locations, indicating that in certain years droughts can affect the entire country. The extreme south of Zambia is the most prone to drought.
•Current nexus thinking is limited to water, energy, and food as resources.•As a fundamental conceptual framing, the nexus must include the environment.•In the social–ecological systems framework, ...the nexus framework enhances options to adapt to global change.•Our re-conceptualized nexus framework integrates adaptive capacity and the water–energy–food (WEF) resource nexus.•The nexus concept should acknowledge and incorporate bi-directional drivers of earth systems and planetary boundary thresholds.
The water–energy–food nexus has emerged as a productive discourse and methodology in academic research, science-policy dialogues, and development agendas. While the nexus provides a robust framework for interdisciplinary study, research remains focused on synergies and tradeoffs in resource ‘security’ and fails to adequately acknowledge the environment as the set of natural processes underpinning the nexus, particularly interactions among water, energy, and food. Resource security as a reductionist discourse does not address the limitations and potential of natural processes and the dynamic nature of human processes, especially adaptation to global change. A review of recent literature highlights the need to redefine the nexus to fundamentally incorporate the environment, and, drawing on social–ecological systems thinking, to integrate considerations of adaptive capacity and resilience within nexus theory and practice. Future directions for this line of inquiry include identifying feasible ways of assessing the nexus in the context of dynamic social and ecological systems, and implications that adaptive actions have across resource-use sectors and the environment. A more holistic nexus framework enhances our options to manage environmental interactions, human activities, and policies to adapt to global-change uncertainties.
Since the impacts of climate change will be felt most directly through changes in water availability and water security, adequate tools are required to support water resources management decisions ...for the medium and long term. The Climate Risk Informed Decision Analysis (CRIDA) provides a pathway for more localized vulnerability assessments of water resources under climate change, while encompassing the uncertainty of current global climate projections. Within this framework, this paper demonstrates a climate stress test to identify changes in key performance indicators defined through local stakeholder consultations using a bottom-up approach. When applied to a case study in the Limari River basin in Chile, the stress test highlights the vulnerability of the reservoir system to climate variability and change, through a comprehensive analysis of 43 Global Circulation Models, of which 34 were retained. The Level of Concern (LoC) was defined as high, due to a high plausibility for entering into adverse water security conditions, that are expected to provoke a significant impact in the highly productive areas of the watershed. As demonstrated by the case study, the climate stress test provides a relevant assessment tool for potential climate change impacts on critical components of the water system in vulnerable catchments.
The classical determination of the soil water retention curve (SWRC) by measuring soil water content at different matric potentials ψ using undisturbed soil samples is time consuming and expensive. ...Furthermore, undisturbed soil sampling can be an intricate task when coarse soil fragments (>2 mm) are present. The objective of this study was to test whether tension infiltrometry could be used to estimate the SWRC of stony soils and to investigate to what extent the coarse fragments affected the SWRC. Tension infiltrometer measurements were conducted at 44 sites with stony soils in arid Chile. Soil water retention curves obtained through inverse modeling were compared with laboratory-determined water retention (theta, omega) data pairs. Differences were found to be small, confirming the applicability of the inverse modeling method. Rock fragments had a significant indirect influence on water retention for matric potentials higher than -0.30 kPa, which could be attributed to their direct influence on pore size distribution.
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► Mean Annual Precipitation was used as criteria for homogeneous region formation. ► A special case of the Kappa distribution was found to fit best to annual precipitation. ► New ...tools were developed to handle regional frequency analysis based on L-moments. ► Spatially continuous drought return period maps were constructed. ► The importance of homogeneity for proper probability model selection in arid zones was confirmed.
Droughts are among the most important natural disasters, particularly in the arid and semiarid regions of the world. Proper management of droughts requires knowledge of the expected frequency of specific low magnitude precipitation totals for a variety of durations. Probabilistic approaches have often been used to estimate the average recurrence period of a given drought event. However, probabilistic model fitting by conventional methods, such as product moment or maximum likelihood in areas with low availability of long records often produces highly unreliable estimates. Recognizing the need for adequate estimates of return periods of severe droughts in the arid and semiarid region of Chile, a regional frequency analysis method based on L-moments (RFA-LM) was used for estimating and mapping drought frequency. Some adaptations to the existing procedures for forming homogeneous regions were found necessary. In addition, a new 3-parameter distribution, the Gaucho, which is a special case of the 4-parameter Kappa distribution, was introduced, and the analysis procedure was improved by the developments of two new software tools named L-RAP, to perform the RFA-LM analysis, and L-MAP, to map the resulting drought maps. Eight homogeneous sub-regions were delineated using the Gaucho distribution and used to construct return period maps for drought events with 80% and 40% precipitation of the normal. The study confirms the importance of a sub-regional homogeneity test, and the usefulness of the Gaucho distribution. The RFA-LM showed that droughts with a 40% precipitation of the normal have return periods that range from 4
years at the northern arid boundary of the study area to 22
years at the southern sub-humid boundary. The results demonstrate the need for different thresholds for declaring a drought than those currently in use for drought characterization in north-central Chile.
Infiltration measurements in arid, stony soils are notoriously variable in visually homogeneous areas, and have been reported to be influenced by embedded stone fragments. This study aimed to ...identify the influence of rock fragment contents, orientation, and position within a small arid watershed on hydraulic conductivity in northern Chile. Two different measurement techniques were used, a single-ring infiltrometer with constant ponding head and a tension infiltrometer, which were applied at both an undisturbed field site (44 locations along three transects) and on the disturbed <2-mm soil fraction from the same locations. Variations in saturated and unsaturated hydraulic conductivities were observed when using different calculation methods, adding to the observed variability. For saturated conditions, only small differences in conductivities were observed between two calculation methods, whereas unsaturated hydraulic conductivities calculated by five different methods showed more important variations. Stone fragment content correlated significantly with both saturated and unsaturated conductivities, probably due to a positive correlation between stone content and coarse lacunar pore space. Slope orientations with higher amounts of stone fragments gave higher infiltration rates, as well as transects with steeper slopes and more, but smaller, rock fragments. When evaluating differences in infiltration rates observed along three transects in the watershed, variability could be mainly attributed to stone fragment content influences.
In arid and semi-arid zones, runoff harvesting techniques are often applied to increase the water retention and infiltration on steep slopes. Additionally, they act as an erosion control measure to ...reduce land degradation hazards. Nevertheless, few efforts were observed to quantify the water harvesting processes of these techniques and to evaluate their efficiency. In this study, a combination of detailed field measurements and modelling with the HYDRUS-2D software package was used to visualize the effect of an infiltration trench on the soil water content of a bare slope in northern Chile. Rainfall simulations were combined with high spatial and temporal resolution water content monitoring in order to construct a useful dataset for inverse modelling purposes. Initial estimates of model parameters were provided by detailed infiltration and soil water retention measurements. Four different measurement techniques were used to determine the saturated hydraulic conductivity (Ksat) independently. The tension infiltrometer measurements proved a good estimator of the Ksat value and a proxy for those measured under simulated rainfall, whereas the pressure and constant head well infiltrometer measurements showed larger variability. Six different parameter optimization functions were tested as a combination of soil-water content, water retention and cumulative infiltration data. Infiltration data alone proved insufficient to obtain high model accuracy, due to large scatter on the data set, and water content data were needed to obtain optimized effective parameter sets with small confidence intervals. Correlation between the observed soil water content and the simulated values was as high as R2=0.93 for ten selected observation points used in the model calibration phase, with overall correlation for the 22 observation points equal to 0.85. The model results indicate that the infiltration trench has a significant effect on soil-water storage, especially at the base of the trench.
Infiltration measurements to determine the field saturated hydraulic conductivity (K(fs)) in arid lands are often plagued by large variations that can be attributed to soil heterogeneity, the ...measurement method, the number of replications, and the K(fs) calculation method used. This study addressed the question of how comparable are two different measurement methods, the single-ring infiltrometer (SR) and double-ring infiltrometer (DR), when applied at three locations in a semiarid part of Chile that show moderate (15%) to high (55%) stoniness. Additionally, K(fs) variations due to different calculation methods for the same measurement method were thoroughly investigated, considering nine methods for the SR and 10 methods for the DR. Results showed that different calculation techniques gave sometimes significantly different estimates of K(fs) when using the same data set, and those relative differences were conserved between measurement locations. When comparing the same calculation technique for both SR and DR, both methods gave equivalent K(fs) estimates for each location. The SR infiltration measurements were modeled better using a transient approach, while infiltration models considering steady state performed better with the DR.
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