Hydrological Sensitivity Research Articles

Relevance and Scale Dependence of Hydrological Changes in Glacierized Catchments: Insights from Historical Data Series in the Eastern Italian Alps

Glaciers have an important hydrological buffering effect, but their current rapid reduction raises concerns about future water availability and management. This work presents a hydrological sensitivity analysis to different climatic and glacier cover conditions, carried out over four catchments with area between 8 and 1050 km2, and with glacierization between 2% and 70%, in the Italian Alps. The analysis is based on past observations, and exploits a unique dataset of glacier change and hydro-meteorological data. The working approach is aimed at avoiding uncertainties typical of future runoff projections in glacierized catchments. The results highlight a transition from glacial to nival hydrological regime, with the highest impacts in August runoff over smaller catchments. The buffering effect of current glaciers has largely decreased if compared to the Little Ice Age, up to 75% for larger catchments, but it is still important during warm and dry summers like 2003. We confirm a non-linear relationship between glacier contribution in late summer and catchment area/percent glacierization. The peak in runoff attributable to glacier melt, expected in the next 2–3 decades on highly glacierized alpine catchments, has already passed in the study area.

Heterogeneous parallel computing accelerated generalized likelihood uncertainty estimation (GLUE) method for fast hydrological model uncertainty analysis purpose

The generalized likelihood uncertainty estimation (GLUE) is a famous and widely used sensitivity and uncertainty analysis method. It provides a new way to solve the “equifinality” problem encountered in the hydrological model parameter estimation. In this research, we focused on the computational efficiency issue of the GLUE method. Inspired by the emerging heterogeneous parallel computing technology, we parallelized the GLUE in algorithmic level and then implemented the parallel GLUE algorithm on a multi-core CPU and many-core GPU hybrid heterogeneous hardware system. The parallel GLUE was implemented using OpenMP and CUDA software ecosystems for multi-core CPU and many-core GPU systems, respectively. Application of the parallel GLUE for the Xinanjiang hydrological model parameter sensitivity analysis proved its much better computational efficiency than the traditional serial computing technology, and the correctness was also verified. The heterogeneous parallel computing accelerated GLUE method has very good application prospects for theoretical analysis and real-world applications.

Calibration of a hydrological model and sensitivity analysis of its parameters: a case study of Seonath river basin

The objective of this paper is surface runoff estimation of the Seonath river basin using a semi-distributed hydrological model, i.e., soil and water assessment tool (SWAT). In this paper, the study on calibration and sensitivity is carried out using SWAT-CUP (calibration and uncertainty program) along with sequential uncertainty fitting (SUFI-2) algorithm. The performance of SWAT model is evaluated by various statistical measures; such as Nash-Sutcliffe (NS) coefficient, coefficient of determination (R2), percent bias (Pbias), p factor, r factor and ratio of the root-mean-square error (RMSE) to the standard deviation of the observation (RSR). In the current work, 31 years (1980-2010) of weather data was used. The time slice for model calibration was 15 years, i.e., 1987-2001 with seven years of warming period 1980-1986 and validation period was comprised of nine years (2002-2010). In the study, the calibration of the model was done for the two stations which is a major step for carrying out further study related to climate and land use change impact assessment. The study yielded satisfactory results in terms of model performance.

Calibration of a hydrological model and sensitivity analysis of its parameters: a case study of Seonath river basin

Calibration of a hydrological model and sensitivity analysis of its parameters: a case study of Seonath river basin

Drivers of Precipitation Change: An Energetic Understanding

AbstractThe response of the hydrological cycle to climate forcings can be understood within the atmospheric energy budget framework. In this study precipitation and energy budget responses to five forcing agents are analyzed using 10 climate models from the Precipitation Driver Response Model Intercomparison Project (PDRMIP). Precipitation changes are split into a forcing-dependent fast response and a temperature-driven hydrological sensitivity. Globally, when normalized by top-of-atmosphere (TOA) forcing, fast precipitation changes are most sensitive to strongly absorbing drivers (CO2, black carbon). However, over land fast precipitation changes are most sensitive to weakly absorbing drivers (sulfate, solar) and are linked to rapid circulation changes. Despite this, land-mean fast responses to CO2 and black carbon exhibit more intermodel spread. Globally, the hydrological sensitivity is consistent across forcings, mainly associated with increased longwave cooling, which is highly correlated with intermodel spread. The land-mean hydrological sensitivity is weaker, consistent with limited moisture availability. The PDRMIP results are used to construct a simple model for land-mean and sea-mean precipitation change based on sea surface temperature change and TOA forcing. The model matches well with CMIP5 ensemble mean historical and future projections, and is used to understand the contributions of different drivers. During the twentieth century, temperature-driven intensification of land-mean precipitation has been masked by fast precipitation responses to anthropogenic sulfate and volcanic forcing, consistent with the small observed trend. However, as projected sulfate forcing decreases, and warming continues, land-mean precipitation is expected to increase more rapidly, and may become clearly observable by the mid-twenty-first century.

Comparison of the Fast and Slow Climate Response to Three Radiation Management Geoengineering Schemes

AbstractGeoengineering has been proposed as a backup approach to rapidly cool the Earth and avoid damages associated with anthropogenic climate change. In this study, we use the NCAR Community Earth System Model to conduct a series of slab‐ocean and prescribed sea surface temperature simulations to investigate the climate response to three proposed radiation management geoengineering schemes: stratospheric aerosol increase (SAI), marine cloud brightening (MCB), and cirrus cloud thinning (CCT). Our simulations show that different amounts of radiative forcing are needed for these three schemes to compensate global mean warming induced by a doubling of atmospheric CO2. With radiative forcing defined in terms of top‐of‐atmosphere energy imbalances in prescribed sea surface temperature simulations with land temperature adjustments, radiative forcing efficacy for SAI is about 15% smaller than that of CO2, and the efficacy for MCB and CCT is about 10% larger than that of CO2. In our simulations, different forcing efficacies are associated with different feedback processes for these forcing agents. Also, these geoengineering schemes produce different land‐ocean temperature change contrasts. The apparent hydrological sensitivity, that is, change in equilibrium global mean precipitation per degree of equilibrium temperature change, differs substantially between CO2, SAI, MCB, and CCT forcings, which is mainly a result of different precipitation responses during fast adjustment. After removing the component of fast adjustment, the northward movement of the Intertropical Convergence Zone in response to these forcing agents is tightly related with changes in the interhemispheric energy exchange and hemispheric temperature gradient.

Climate variability on the Adriatic seaboard during the last glacial inception and MIS 5c from Frasassi Cave stalagmite record

A stalagmite (FR16) from Frasassi Cave, located near the Adriatic coast of the Italian peninsula, offers a 16 kyr petrographic and stable isotope record spanning from 112.8 ± 1.5 ka to 96.6 ± 1.0 ka, corresponding to the interval from marine isotope stage (MIS) 5c to MIS 5d. The physical characteristics of FR16 calcite, allowed for a thorough understanding of the processes controlling isotopic changes, because fabrics as well are controlled by the environmental parameters within the cave that reflect external climate forcing. The FR16 δ13C profile matches fabric changes where columnar fabric usually corresponds to more negative values and micrite/microsparite layers to less negative δ13C values, and with the North Greenland Ice-core Project (NGRIP) δ18O record with more negative δ13C values during interstadials GI24 and GI23. This suggests a hydrological sensitivity for the two proxies, and their variability can be linked to recharge changes. On the other hand, the response to Greenland events appears subdued in the δ18O record and the trend mimics instead the Northern Hemisphere (NH) summer insolation with more negative δ18O values corresponding to the maximum insolation centred at ca. 105 ka. This behaviour can be explained by the higher sensitivity of δ18O to rainfall seasonality, moisture source and trajectories, whose combined effect attenuated the stadials/intersadials signal in the stalagmite.

On the Connection Between Global Hydrologic Sensitivity and Regional Wet Extremes

AbstractA highly uncertain aspect of anthropogenic climate change is the rate at which the global hydrologic cycle intensifies. The future change in global‐mean precipitation per degree warming, or hydrologic sensitivity, exhibits a threefold spread (1–3%/K) in current global climate models. In this study, we find that the intermodel spread in this value is associated with a significant portion of variability in future projections of extreme precipitation in the tropics, extending also into subtropical atmospheric river corridors. Additionally, there is a very tight intermodel relationship between changes in extreme and nonextreme precipitation, whereby models compensate for increasing extreme precipitation events by decreasing weak‐moderate events. Another factor linked to changes in precipitation extremes is model resolution, with higher resolution models showing a larger increase in heavy extremes. These results highlight ways various aspects of hydrologic cycle intensification are linked in models and shed new light on the task of constraining precipitation extremes.

Contributions of climate change and anthropogenic activities to runoff change in the Hongshui River, Southwest China

Changes in water resources are mainly affected by the combined effects of anthropogenic activities and climate change. The relative effects of anthropogenic activities and climate on a river basin are investigated to not only understand the hydrological response mechanism in a catchment but also manage local water resources and protect against floods and droughts. In this study, a variable infiltration capacity (VIC) model combined with a hydrologic sensitivity analysis was used to quantify the effects of anthropogenic activities and climate change on runoff in the upper reaches of the Hongshui River basin (UHRB). During 1970-2015, the runoff contribution for climate change and anthropogenic activities were 89.2% and 10.8%, respectively. This result suggests that climate is the major driver of runoff variation in the basin. However, during 1990-1999, anthropogenic activities played a decisive role in the reduction in streamflow, and the contribution percentage was 96.35%. Moreover, the impact of anthropogenic activities on runoff changed from positive to negative from the 1980s to the 2000s, and the negative effect showed a continuously increasing trend. Hydrologic sensitivity methods and hydrological modelling produced similar estimates. Our findings emphasize that the impacts of anthropogenic activities such as land use change and the operations of water conservancy projects should be properly managed.

Observed High-Latitude Precipitation Amount and Pattern and CMIP5 Model Projections

Utilizing reanalysis and high sensitivity W-band radar observations from CloudSat, this study assesses simulated high-latitude (55–82.5°) precipitation and its future changes under the RCP8.5 global warming scenario. A subset of models was selected based on the smallest discrepancy relative to CloudSat and ERA-I reanalysis using a combined ranking for bias and spatial root mean square error (RMSE). After accounting for uncertainties introduced by internal variability due to CloudSat’s limited four year day-night observation period, RMSE provides greater discrimination between the models than a typical mean state bias criterion. Over 1976–2005 to 2071–2100, colder months experience larger fractional modelled precipitation increases than warmer months, and the observation-constrained models generally report a larger response than the full ensemble. For everywhere except the Southern Hemisphere (SH55, for 55–82.5°S) ocean, the selected models show greater warming than the model ensemble while their hydrological sensitivity (fractional precipitation change with temperature) is indistinguishable from the full ensemble relationship. This indicates that local thermodynamic effects explain much of the net high-latitude precipitation change. For the SH ocean, the models that perform best in the present climate show near-median warming but greater precipitation increase, implying a detectable contribution from processes other than local thermodynamic changes. A Taylor diagram analysis of the full CMIP5 ensemble finds that the Northern Hemisphere (NH55) and SH55 land areas follow a “wet get wetter” paradigm. The SH55 land areas show stable spatial correlations between the simulated present and future climate, indicative of small changes in the spatial pattern, but this is not true of NH55 land. This shows changes in the spatial pattern of precipitation changes through time as well as the differences in precipitation between wet and dry regions.

Quantifying impacts of climate variability and human activities on the streamflow of an Alpine river

In this study, we present a review of the current state-of-the-art research on streamflow alteration assessment, and examine the impact of climate variability and human activities on the natural streamflow of a tributary of Lake Maggiore (north-western Italy). The recent concept of climate elasticity of streamflow was used to indicate in which parameters the streamflow is more sensitive. First, a statistically identified change point was used to define the base period. Methods including hydrological sensitivity, climate elasticity and hydrological modelling then allowed us to estimate the anthropogenic and climatic effects on streamflow and to have an idea of the complicated non-linear relationship among streamflow, precipitation and temperature. Our results suggest that climate variability accounted for 85% of the decrease in streamflow. The remaining change could result from land cover-use change. The climate elasticity method used in this study could predict streamflow for future climatic change scenarios.

Reconstruction of the Water Cultivation Paleoenvironment Dating Back to the Han and Tang Dynasties Surrounding the Yangguan Frontier Pass Using X- and L-Band SAR Data

Supported by a shallow groundwater wetland ecosystem, the Nanhu oasis, which is the location of the Yangguan frontier pass, represents an important supply and defence station for the ancient Silk Road. The reconstruction of the evolution of the water cultivation environment is helpful for archaeological surveys and the protection of this well-known heritage site. This study proposes a workflow for reconstructing the water cultivation paleoenvironment-based primarily on X- and L-band spaceborne synthetic aperture radar (SAR) data. First, TerraSAR-X/TanDEM-X (TSX/TDX)-generated Digital Elevation Model (DEM) data were used for microrelief analyses, including a watershed analysis and drainage network extraction. Several dried-up paleochannels and the range of the Daze (a wetland dating back to the Tang Dynasty (618–907 A.D.)) were identified. Second, based on the hydrological sensitivity analysis of the multi-temporal L-band SAR data, arid land vegetation accompanying the emergence of groundwater was extracted to locate ancient arable areas using backscattering and coherence characteristics. Finally, reconstruction of the water cultivation paleoenvironment surrounding the Nanhu oasis dating back to the Han and Tang dynasties (202 B.C.–907 A.D.) was performed, referring to historical documents. New discoveries were validated by field campaigns, and the results of the SAR archaeological investigations conducted in this study indicated that the ancient arable area in the Nanhu oasis was nearly double the current dimensions.

Low clouds link equilibrium climate sensitivity to hydrological sensitivity

Equilibrium climate sensitivity (ECS) and hydrological sensitivity describe the global mean surface temperature and precipitation responses to a doubling of atmospheric CO2. Despite their connection via the Earth’s energy budget, the physical linkage between these two metrics remains controversial. Here, using a global climate model with a perturbed mean hydrological cycle, we show that ECS and hydrological sensitivity per unit warming are anti-correlated owing to the low-cloud response to surface warming. When the amount of low clouds decreases, ECS is enhanced through reductions in the reflection of shortwave radiation. In contrast, hydrological sensitivity is suppressed through weakening of atmospheric longwave cooling, necessitating weakened condensational heating by precipitation. These compensating cloud effects are also robustly found in a multi-model ensemble, and further constrained using satellite observations. Our estimates, combined with an existing constraint to clear-sky shortwave absorption, suggest that hydrological sensitivity could be lower by 30% than raw estimates from global climate models. The connections between global mean temperature and precipitation responses to CO2 doubling (equilibrium climate and hydrological sensitivity) are driven through low-cloud responses to surface warming, according to MIROC5 perturbation experiments.

How Well Does the Mechanistic Water Quality Model CE‐QUAL‐W2 Represent Biogeochemical Responses to Climatic and Hydrologic Forcing?

AbstractMechanistic water quality models are applied globally for water quality management in rivers and lakes. However, it is unclear how well these models represent the response of lakes to changes in climate and hydrologic conditions. To address this question, we conducted a series of climate and hydrologic sensitivity analyses using a parameterized water quality model, CE‐QUAL‐W2, for the Spokane River and Lake Spokane system. Two experimental tests with climate and flow forcing showed that the model predictions were rather insensitive to climatic‐driven hydrologic changes and a wide range of hydrologic conditions (1st to 99th percentile flows) for two different wastewater treatment plant discharge scenarios. The model realistically represented some aspects of Lake Spokane's observed responses to climatic and hydrologic variability, for example, the water residence time and some water quality trends. However, the model overestimated the reservoir total phosphorus (TPR) concentration by ~37% and the chlorophyll a (Chl a) concentration by ~31% and underestimated the minimum volume‐weighted hypolimnetic dissolved oxygen (DOMIN) concentration by ~26% for a wide range of flows compared to the observed data. In contrast to the model's water quality insensitivity, the modeled temperature was more sensitive to flow than was actually observed in Lake Spokane. This study provides guidance for improving the response of one of the most important mechanistic water quality models to climatic and hydrologic forcing and should help modelers and decision‐makers to develop a rigorous assessment of climate and flow sensitivity to improve the margin of safety when setting total maximum daily load targets.

Sensitivity of streamflow to climate change in California

Climate change is rapidly altering the global water cycle, exposing vulnerabilities in both social and environmental systems. However, uncertainty in future climate predictions makes it difficult to design and evaluate strategies for building climate resilience. In regions such as California, characterized by stressed water-supply systems, high natural climate variability, and substantial uncertainty in future precipitation projections, alternative approaches to assessing climate risks may be useful. Here, we develop a hydrologic sensitivity approach to estimate regional streamflow responses to climate change in California. We use statistical models to predict monthly streamflow from physical catchment features and evaluate how flow changes with incremental changes in precipitation and temperature. The results indicate unique regional and monthly flow responses to climate change, with early summer flows (May–July) in interior mountain region having the greatest sensitivity to temperature and winter flows (December–March) in the xeric region having the greatest sensitivity to precipitation. When evaluated over the range of global climate model projections for mid-century (2040–2069), models generally suggest shifts in streamflow regimes towards higher wet season flows and lower dry season flows relative to historical conditions. The sensitivity analysis provides insight into catchment- and regional-scale hydrologic responses in California and complements other approaches for understanding the consequences of climatic change for water and risk management.

A PDRMIP multi-model study on the impacts of regional aerosol forcings on global and regional precipitation.

Atmospheric aerosols such as sulfate and black carbon (BC) generate inhomogeneous radiative forcing and can affect precipitation in distinct ways compared to greenhouse gases (GHGs). Their regional effects on the atmospheric energy budget and circulation can be important for understanding and predicting global and regional precipitation changes, which act on top of the background GHG-induced hydrological changes. Under the framework of the Precipitation Driver Response Model Inter-comparison Project (PDRMIP), multiple models were used for the first time to simulate the influence of regional (Asian and European) sulfate and BC forcing on global and regional precipitation. The results show that, as in the case of global aerosol forcing, the global fast precipitation response to regional aerosol forcing scales with global atmospheric absorption, and the slow precipitation response scales with global surface temperature response. Asian sulphate aerosols appear to be a stronger driver of global temperature and precipitation change compared to European aerosols, but when the responses are normalised by unit radiative forcing or by aerosol burden change, the picture reverses, with European aerosols being more efficient in driving global change. The global apparent hydrological sensitivities of these regional forcing experiments are again consistent with those for corresponding global aerosol forcings found in the literature. However, the regional responses and regional apparent hydrological sensitivities do not align with the corresponding global values. Through a holistic approach involving analysis of the energy budget combined with exploring changes in atmospheric dynamics, we provide a framework for explaining the global and regional precipitation responses to regional aerosol forcing.

Hydrologic variability and sensitivity based on Hurst coefficient and Bartels statistic

Due to the global climate change and frequent human activities in recent years, the pure stochastic components of hydrological sequence is mixed with one or several of the variation ingredients, including jump, trend, period and dependency. It is urgently needed to clarify which indices should be used to quantify the degree of their variability. In this study, we defined the hydrological variability based on Hurst coefficient and Bartels statistic, and used Monte Carlo statistical tests to test and analyze their sensitivity to different variants. When the hydrological sequence had jump or trend variation, both Hurst coefficient and Bartels statistic could reflect the variation, with the Hurst coefficient being more sensitive to weak jump or trend variation. When the sequence had period, only the Bartels statistic could detect the mutation of the sequence. When the sequence had a dependency, both the Hurst coefficient and the Bartels statistics could reflect the variation, with the latter could detect weaker dependent variations. For the four variations, both the Hurst variability and Bartels variability increased with the increases of variation range. Thus, they could be used to measure the variation intensity of the hydrological sequence. We analyzed the temperature series of different weather stations in the Lancang River basin. Results showed that the temperature of all stations showed the upward trend or jump, indicating that the entire basin had experienced warming in recent years and the temperature variability in the upper and lower reaches was much higher. This case study showed the practicability of the proposed method.

Structuring forces and β-diversity of benthic diatom metacommunities in soda pans of the Carpathian Basin

ABSTRACTSmall soda lakes represent one of the most vulnerable ecosystem types due to their high hydrological sensitivity to climate change and anthropogenic interventions. Since diatoms are excellent bioindicators, determining the β-diversity and the structuring dynamics of diatom metacommunities can provide valuable information for conservation planning for soda pans. In this study, two diatom metacommunities were surveyed monthly during a one-year period from distinct regions of the Carpathian basin: the Fertő-Hanság National Park (FH) between 2013 and 2014, and the Danube-Tisza Interfluve (DT) between 2014 and 2015. We explored whether β-diversity of diatom assemblages in the two regions is enhanced by species turnover or nestedness (related to richness differences) and investigated the role of deterministic and stochastic processes in shaping β-diversity patterns. Furthermore, we evaluated the contribution of environmental variables, geographic distance and temporal variation to community structure. High β-diversity (>90%) was revealed for both metacommunities, and was maintained primarily by species turnover. Within the metacommunity of the DT where the natural hydrological cycle of soda pans is not disturbed, diatom communities assembled mainly due to the selection force of environment at a spatiotemporal scale. In the soda pans located in the habitat reconstruction area of the FH, besides species-sorting, significant temporal variation in community structure appeared as a result of water management and periodic water supply. Our results point to the need for a conservation management strategy which maintains the natural hydrological regime of small saline lakes, and therefore their habitat heterogeneity which is of high conservation value.

Assessing the impacts of land use on downstream water quality using a hydrologically sensitive area concept

Understanding the relationship between land use and water quality is essential to improve water quality through carefully managing landscape change. This study applies a linear mixed model at both watershed and hydrologically sensitive areas (HSAs) scales to assess such a relationship in 28 northcentral New Jersey watersheds located in a rapidly urbanizing region in the United States. Two models differ in terms of the geographic scope used to derive land use matrices that quantify land use conditions. The land use matrices at the watershed and HSAs scales represent the land use conditions in these watersheds and their HSAs, respectively. HSAs are the hydrological “hotspots” in a watershed that are prone to runoff generation during storm events. HSAs are derived using a soil topographic index (STI) that predicts hydrological sensitivity of a landscape based on a variable source area hydrology concept. The water quality indicators in these models are total nitrogen (TN), total phosphorus (TP) and total suspended solids (TSS) concentrations in streams observed at the watershed outlets. The modeling results suggest that presence of low density urban land, agricultural land and wetlands elevate while forest decreases TN, TP and/or TSS concentrations in streams. The watershed scale model tends to emphasize the role of agricultural lands in water quality degradation while the HSA scale model highlights the role of forest in water quality improvement. This study supports the hypothesis that even though HSAs are relatively smaller area compared to watershed, still the land uses within HSAs have similar impacts on downstream water quality as the land uses in entire watersheds, since both models have negligible differences in model evaluation parameters. Inclusion of HSAs brings an interesting perspective to understand the dynamic relationships between land use and water quality.

Linear and Nonlinear Hydrological Cycle Responses to Increasing Sea Surface Temperature

AbstractAn effective mechanism for determining tropical rainfall patterns in response to sea surface temperature (SST) increases with varying magnitude and horizontal distribution has not been developed thus far in climate change studies. In order to examine changes in precipitation pattern with increasing SST, we conducted a series of atmospheric general circulation model experiments using a 30 year record of observed SST for which either globally uniform SST increases of 1 K, 2 K, and 4 K or El Niño/La Niña‐like patterned SST anomaly has been imposed. Although the global‐mean precipitation linearly increases with the SST increase irrespective of its spatial distribution, regional precipitation changes were found to occur nonlinearly depending on the magnitude of the uniform SST increase. Owing to nonlinearity in the atmospheric circulation response, the regional hydrological sensitivity was larger with a smaller increase in SST. The precipitation response to the SST pattern was, however, quasi‐linear to the magnitude of the SST change and can be separated from the response to the uniform SST increase. This study thus emphasizes the importance of relative amplitudes of uniform and structured SST increases for future rainfall projection.