Ecohydrological System Research Articles

Response of Water Quality to Land Use and Landscape Pattern in the Ganjiang River Watershed.

Analysing the impact of landscape composition and structure on water quality at different scales is of great significance to water quality protection. The aim of this study was to determine scale-dependent impacts of land use/landscape patterns on water quality. The Ganjiang River, the largest water system in the Poyang Lake watershed, the largest freshwater lake in China. The response of water quality to land use and landscape patterns in the Ganjiang River watershed was explored based on land use and water quality data using redundancy and Spearman correlation analyses. Considering upstream monitoring of the entire Ganjiang River watershed; watersheds at the county level administrative region; and 1, 2, 5, 10, 15, 20, and 30 km-radius circular buffer zones, a total of nine scales of land use/landscape patterns that influence water quality in the Ganjiang River watershed were analysed. Results indicated that the county-level scale and the land use type of the 20 km-radius buffer zone upstream of the monitoring site were closely linked to water quality (96.28% and 93.23%, respectively). Among the land use types, construction land and cultivated land were the main output sources of pollutants. Regarding landscape pattern index, the greater the fragmentation of the landscape, the heavier was the water pollution load; the more the patches per unit area, the more stable was the ecosystem and the lower was the pollutant concentration. In addition, the eco-hydrological system of the Ganjiang River watershed was revealed to some extent through multi-angle analysis. These conclusions can serve as a reference for government departments to formulate land management and water quality protection measures.

Evaluating main drivers of terrestrial water storage depletion in the agro-pastoral ecotone of northern China

With the heightened threat of declining terrestrial groundwater, determining the effects of changing environments on terrestrial water storage anomaly (TWSA) is essential for water resource management. As a critical element of the water cycle, the multi-effects of the natural and artificial factors on TWSA were still not fully understood and quantified. Using multiple high-resolution data products and the structural equation model (SEM), this study discussed how climate, vegetation, and human activities affected terrestrial water storage (TWS) in the West Liao River basin (WLRB), China, from 1990 to 2020. The results confirmed that vegetation showed a greening trend while TWS depleted at 5.93 cm/10a in the WLRB. TWS in greening areas has a negative correlation with vegetation growth. The decline in TWS is mainly dominated by precipitation and runoff variability. By influencing eco-hydrological cycle processes, climate change and human activities affect TWS through direct and indirect(by influencing NDVI) pathways. Land use change, manifested as conversion of grassland into cropland, contributed to the most decline of TWS (51.2 %). Moreover, the crop yield increasing, climate warming, and vegetation greening could lead to TWS depletion. Spatially, the overexploitation of the groundwater for irrigation to support crop production was probably the most critical cause of TWS depletion over upstream of the WLRB. Furthermore, in the West Liao Plain, the intensified vegetation greenness also led to the increasing ecosystem water demand, resulting in the decrease of TWS. This study improves our understanding of the interaction of the basinal eco-hydrological system and provides a hint that reducing groundwater extraction and implementing agriculture fallow is essential to recovering water storage and alleviating the water resource crisis in the agro-pastoral ecotone.

Challenges in studying water fluxes within the soil-plant-atmosphere continuum: A tracer-based perspective on pathways to progress

Tracing and quantifying water fluxes in the hydrological cycle is crucial for understanding the current state of ecohydrological systems and their vulnerability to environmental change. Especially the interface between ecosystems and the atmosphere that is strongly mediated by plants is important to meaningfully describe ecohydrological system functioning. Many of the dynamic interactions generated by water fluxes between soil, plant and the atmosphere are not well understood, which is partly due to a lack of interdisciplinary research. This opinion paper reflects the outcome of a discussion among hydrologists, plant ecophysiologists and soil scientists on open questions and new opportunities for collaborative research on the topic “water fluxes in the soil-plant-atmosphere continuum” especially focusing on environmental and artificial tracers. We emphasize the need for a multi-scale experimental approach, where a hypothesis is tested at multiple spatial scales and under diverse environmental conditions to better describe the small-scale processes (i.e., causes) that lead to large-scale patterns of ecosystem functioning (i.e., consequences). Novel in-situ, high-frequency measurement techniques offer the opportunity to sample data at a high spatial and temporal resolution needed to understand the underlying processes. We advocate for a combination of long-term natural abundance measurements and event-based approaches. Multiple environmental and artificial tracers, such as stable isotopes, and a suite of experimental and analytical approaches should be combined to complement information gained by different methods. Virtual experiments using process-based models should be used to inform sampling campaigns and field experiments, e.g., to improve experimental designs and to simulate experimental outcomes. On the other hand, experimental data are a pre-requisite to improve our currently incomplete models. Interdisciplinary collaboration will help to overcome research gaps that overlap across different earth system science fields and help to generate a more holistic view of water fluxes between soil, plant and atmosphere in diverse ecosystems.

Peatland groundwater level in the Indonesian maritime continent as an alert for El Niño and moderate positive Indian Ocean dipole events

In general, it is known that extreme climatic conditions such as El Niño and positive Indian Ocean Dipole (IOD+) cause prolonged drought in Indonesia's tropical peatlands so that groundwater levels (GWL) drop and peat is prone to fire. However, 27 years of GWL measurements in Central Kalimantan peat forests show the opposite condition, where the lowest GWL occurs several weeks before El Niño and after IOD+ reaches its peaks. We show that the dropped sea surface temperature anomaly induced by anomalously easterly winds along the southern Java-Sumatra occurs several weeks before the GWL drop to the lowest value. Local rainfall decreased, and GWL dropped sharply by 1.0 to 1.5 m, during the super El Niño events in 1997/98 and 2015, as well as remarkable events of IOD+ in 2019. It is suggested that the tropical peatland ecohydrological system (represented by the GWL), El Niño Southern Oscillation (ENSO), and IOD+ are teleconnected. Hence, monitoring GWL variability of peatland over the IMC is a possibility an alert for extreme climate events associated with El Niño and/or moderate IOD+.

Source Relationships and Model Structures Determine Information Flow Paths in Ecohydrologic Models

AbstractIn a complex ecohydrologic system, vegetation and soil variables combine to dictate heat fluxes, and these fluxes may vary depending on the extent to which drivers are linearly or nonlinearly interrelated. From a modeling and causality perspective, uncertainty, sensitivity, and performance measures all relate to how information from different sources “flows” through a model to produce a target, or output. We address how model structure, broadly defined as a mapping from inputs to an output, combines with source dependencies to produce a range of information flow pathways from sources to a target. We apply information decomposition, which partitions reductions in uncertainty into synergistic, redundant, and unique information types, to a range of model cases. Toy models show that model structure and source dependencies both restrict the types of interactions that can arise between sources and targets. Regressions based on weather data illustrate how different model structures vary in their sensitivity to source dependencies, thus affecting predictive and functional performance. Finally, we compare the Surface Flux Equilibrium theory, a land‐surface model, and neural networks in estimating the Bowen ratio and find that models trade off information types particularly when sources have the highest and lowest dependencies. Overall, this study extends an information theory‐based model evaluation framework to incorporate the influence of source dependency on information pathways. This could be applied to explore behavioral ranges for both machine learning and process‐based models, and guide model development by highlighting model deficiencies based on information flow pathways that would not be apparent based on existing measures.

Evaluation and optimization of the water diversion system of ecohydrological restoration megaproject of Tarim River, China, through wavelet analysis and a neural network

Water transfers have been implemented globally as important and effective ecological restoration tools over the last several decades. However, the periodic impacts of large-scale ecological water transport projects (EWTP) on ecohydrological systems have been neglected. In this study, wavelet analysis was used to evaluate the effect of flow regimes of EWTPs on the dynamics of ecohydrological systems through real data from a megaproject in the Tarim River basin, China. The results reveal that comparing with natural stream, the restoration flow exhibits seasonal periodicities in the winter instead of flood season, and exhibits unstable yearly periodicities. These characteristics created a distinct groundwater dynamics, which are not coincident with the growth rhythm of riparian vegetation. To optimize the EWTP, two designed flow schemes based on the time lags between flow and vegetation growth which was estimated using the wavelet analysis at seasonal and annual scales were proposed to improve the ecosystem restoration efficiency. The NARX network was used to predict the ecological restoration result. The predicting results show an up to 40% increase comparing to original restoration flow with the same total water volume. These results provide a new insight on ecohydrological system dynamics under EWTP from the periodic perspective, and also quantitatively prove that the designed flows based on wavelet analysis can improve ecosystem restoration efficiency in EWTPs. The methodologies used in this research are mathematical rigorous and can be widely applied to other EWTPs.

Dynamic 2H irrigation pulse labelling reveals rapid infiltration and mixing of precipitation in the soil and species‐specific water uptake depths of trees in a temperate forest

AbstractUnderstanding the movement of water in terrestrial ecosystems and determining the soil depths from which mature trees take up water has become an important research priority. Here, we test the suitability of a dynamic 2H pulse‐labelling experiment for assessing (1) the fate of a simulated precipitation event as it moves through the ecohydrological system and (2) the water uptake depths of different tree species in a mature temperate forest. We applied 2H‐labelled water as a single pulse to the top soil using a sprinkler system and then allowed it to infiltrate into deeper soil layers by washing it through the soil column with a sequence of non‐2H‐labelled irrigation pulses. We then followed this 2H‐enriched irrigation pulse over a period of 81 days in different depths of the soil and in the xylem of four tree species (Fagus sylvatica, Quercus petraea, Picea abies and Pinus sylvestris). Our experiment shows infiltration and mixing of the irrigation pulse in the soil occurs within a few days. Furthermore, we found that tree species differed significantly in their use of shallow (−10‐ to −30‐cm soil depth) and deep (−80‐cm soil depth) soil water. We also found immediate uptake of infiltrating mobile soil water by trees, which questions the recently established two‐water‐worlds hypothesis. Our study demonstrated that a dynamic 2H‐labelled irrigation pulse is a useful approach to (1) assess how water from a precipitation event infiltrates into a forest ecosystem and (2) assess the water uptake depths of different temperate tree species.

Forest fragmentation and its potential implications for the management of the Tarumã-Açu River basin, Central Amazon, Brazil

The intensification of deforestation and the consequent fragmentation of the natural landscape in urban and periurban watersheds affect the entire eco-hydrological system, increasing the need to understand how these changes can affect their sustainability. In this sense, the present study evaluated the potential implications of forest fragmentation for the management of the Tarumã-Açu basin, based on the characterization of the structural and functional patterns of the landscape. For this, we mapped and categorized the basin’s forest fragments, based on the supervised classification (Bhattacharyya Method) of Landsat/OLI image, and, subsequently, we calculated the landscape metrics (area, density and size, edge, form, core, isolation and connectivity). The metrics showed a very fragmented landscape, especially in the region of the basin's low course, which concentrates the smallest, most dispersed, and vulnerable fragments even in conservation units. The headwater region, on the other hand, has the largest patches, with a large amount of central area and high structural and functional connectivity, which are fundamental for the sustainability of the basin and, therefore, deserve attention and prioritization by managers. The results offer important subsidies and unpublished data that can contribute to elaboration of the basin’s management plan and for the definition of conservation and restoration strategies of the forest remnants, indicating priority areas for the implementation of these actions.

Ecohydrology and causes of peat degradation at the Vasi peatland, South Africa

The Vasi peatland complex is situated in the northeast of South Africa. It is an unprotected area surrounded by pine (Pinus sp.) and blue gum (Eucalyptus sp.) plantations. Little is known about the conditioning factors for the area’s development and causes of degradation. In order to understand the ecohydrological system of this complex, water tables and ionic composition of surface water and groundwater, as well as natural isotopes of oxygen, hydrogen and carbon, were measured. Macrofossils and radiocarbon dating of the peat layer were used to describe the historical environmental conditions. We found that peat accumulation started during the Early Holocene and was initiated by terrestrialisation of inter-dune lakes. Our results also show that the Vasi peatland complex is primarily dependent on a perched water table due to the presence of iron-rich deposits close to the surface (i.e. KwaMbonambi Formation). The Vasi peatland basins appear to be hydrologically connected and some basins show indications of cascading through-flow systems, which means that the water flows from a higher basin to a lower one through the permeable parts of the sand dunes and peat layers. The stratigraphy indicates continuous peat accumulation, and thus that the water table was perennially high for thousands of years, despite evidence of the occasional natural occurrence of fires. We conclude that the most likely cause of the observed signs of degradation is land use change, i.e. the recent establishment of plantations, which affect the groundwater system.

Analysis of River System Structure and Runoff Evolution of Typical Section in Ziya River Plain

In this study, by interpretation method, the density, quantity, length and variation of rivers in Ziya River Plainincreased in the 1960s and 1980s, mainly related to the excavation of small tributaries and canals. By comparing the series of years before and after 1980, the amount of surface water resources in the study area has decreased in the past 30 years. By using cumulative anomaly method and Kendall trend test method, it is found that the annual average runoff of typical cross-section decreases obviously, and the time series sudden change occurs in the late 1970s. The situation of the trunk runoff cut-off and drying-up caused by the river system structure and runoff evolution is evaluated, and the interannual evolution of the eco-hydrological system in Ziya River Plain is obtained.These can provide scientific support for water environment research and water ecological restoration in plain areas.

Ecosystem processes at the watershed scale: Influence of flowpath patterns of canopy ecophysiology on emergent catchment water and carbon cycling

AbstractForest canopy water use and carbon cycling traits (WCT) can vary substantially and in spatially organized patterns, with significant impacts on watershed ecohydrology. In many watersheds, WCT may vary systematically along and between hydrologic flowpaths as an adaptation to available soil water, nutrients, and microclimate‐mediated atmospheric water demand. We hypothesize that the emerging patterns of WCT at the hillslope to catchment scale provide a more resistant ecohydrological system, particularly with respect to drought stress, and the maintenance of high levels of productivity. Rather than attempting to address this hypothesis with species‐specific patterns, we outline broader functional WCT groups and explore the sensitivity of water and carbon balances to the representation of canopy WCT functional organization through a modelling approach. We use a well‐studied experimental watershed in North Carolina where detailed mapping of forest community patterns are sufficient to describe WCT functional organization. Ecohydrological models typically use broad‐scale characterizations of forest canopy composition based on remotely sensed information (e.g., evergreen vs. deciduous), which may not adequately represent the range or spatial pattern of functional group WCT at hillslope to watershed scales. We use three different representations of WCT functional organizations: (1) restricting WCT to deciduous/conifer differentiation, (2) utilizing more detailed, but aspatial, information on local forest community composition, and (3) spatially distributed representation of local forest WCT. Accounting for WCT functional organization information improves model performance not only in terms of capturing observed flow regimes (especially watershed‐scale seasonal flow dynamics) but also in terms of representing more detailed canopy ecohydrologic behaviour (e.g., root zone soil moisture, evapotranspiration, and net canopy photosynthesis), especially under dry condition. Results suggest that the well‐known zonation of forest communities over hydrologic gradients is not just a local adaptation but also provides a property that regulates hillslope to catchment‐scale behaviour of water use and drought resistance.

Variability of earthworm-induced biopores and their hydrological effectiveness in space and time

Earthworms create biopores and thereby increase the susceptibility of soils to preferential flow which, on the one hand, reduces surface runoff and soil erosion, but, on the other hand, enhances vertical water and solute transport. Spatial and temporal variability in earthworm abundances might lead to spatial and temporal variability in biopore densities and even in the hydrological effectiveness of these pores. In this paper, we present a reproducible sampling design for simultaneous earthworm-biopore observations and analyze the temporal variability in earthworm abundances, biopore densities and hydrological effectiveness of biopores and its differences between grassland and arable land. During one year we performed six field campaigns where we sampled earthworms and performed dye tracer experiments in the small Luxembourgian Wollefsbach catchment (4.4 km²) on three arable land sites and three grasslands. We quantified how abundances of ecological groups of earthworms affect biopore densities and hydrological effectiveness. Finally, we applied piecewise structural equation modeling (piecewise SEM) to find the most probable structure of the ecohydrological system of soil moisture, clay content, earthworms, biopore densities and their hydrological effectiveness.Our results show that earthworm abundance and biopore density as well as their hydrological effectiveness vary strongly between seasons and between grassland and arable land (0–300 earthworms m−2, 0–500 biopores m−2, 0–100% hydrologically effective biopores). Piecewise SEMs indicate that the temporal variability in earthworm abundances, biopore densities and hydrological effectiveness is significantly affected by two-month averaged soil moisture variability. We also found a significant effect of earthworm abundances on biopore densities and their hydrological effectiveness in 3 and 10 cm depth.Based on these results we recommend the consideration of spatial and temporal variability in biopore densities and their hydrological effectiveness for the reliable representation of macropore flow and related solute transport in soil hydrological models.

Effects of damming and climatic change on the eco-hydrological system: A case study in the Yalong River, southwest China

Abstract The eco-hydrological system in China is undergoing dramatic changes in recent decades due to climate change and construction of cascade dams for power production. Given that multiple drivers often interact in complex and nonadditive ways, the purpose of this study is to predict future changes in runoff and fish habitat quality of the Yalong River basin attributed to the individual and combined effects of cascade dam construction and climate change. The bias corrected and spatially downscaled CMIP5 GCM projections are used to drive the Soil and Water Assessment Tool hydrological model and to simulate and predict runoff responses under diverse scenarios. The physical habitat simulation model is established to describe the relationship between river hydrology and fish habitat quality and to assess the individual and combined effects of cascade dam construction and climate change. The mean annual temperature and precipitation of the Yalong River in 2020–2100 are predicted to increase at a rate of 0.016–0.487 °C/10a and 4.55–10.13 mm/10a, with an increase of 1.63–3.25 °C and 0.66–3.34% in comparison with those in 1957–2012, respectively. While, the mean annual runoff of the middle and lower reaches is increased by 11.77%–16.63% and 14.02%–19.02% compared with that in the history, respectively. The construction of cascade dams could significantly improve the fish habitat quality of the Yalong River basin, especially in dry seasons, and consequently the ecological conservation degree is increased by about 2%. In the middle reaches, changes in runoff from February to October are mainly determined by cascade dam construction, but the effect of climate change becomes more pronounced from November to January. Similarly, cascade dam construction has a more significant effect on runoff of the lower reaches than climate change except in November and December.

Role of Groundwater in the Dryland Ecohydrological System: A Case Study of the Heihe River Basin

Key Points Shallow groundwater (<10 m deep) of alluvial plain responds to land surface regimes and dominates seasonal water budget variations Groundwater system in mountainous upstream impacts the evapotranspiration and surface‐groundwater interactions in alluvial plain downstream Groundwater sustains ecosystem by contributing to evapotranspiration of vegetation in the growing season and buffering lateral flow

Future changes in Yuan River ecohydrology: Individual and cumulative impacts of climates change and cascade hydropower development on runoff and aquatic habitat quality

The eco-hydrological system in southwestern China is undergoing great changes in recent decades owing to climate change and extensive cascading hydropower exploitation. With a growing recognition that multiple drivers often interact in complex and nonadditive ways, the purpose of this study is to predict the potential future changes in streamflow and fish habitat quality in the Yuan River and quantify the individual and cumulative effect of cascade damming and climate change. The bias corrected and spatial downscaled Coupled Model Intercomparison Project Phase 5 (CMIP5) General Circulation Model (GCM) projections are employed to drive the Soil and Water Assessment Tool (SWAT) hydrological model and to simulate and predict runoff responses under diverse scenarios. Physical habitat simulation model is established to quantify the relationship between river hydrology and fish habitat, and the relative change rate is used to assess the individual and combined effects of cascade damming and climate change. Mean annual temperature, precipitation and runoff in 2015–2100 show an increasing trend compared with that in 1951–2010, with a particularly pronounced difference between dry and wet years. The ecological habitat quality is improved under cascade hydropower development since that ecological requirement has been incorporated in the reservoir operation policy. As for middle reach, the runoff change from January to August is determined mainly by damming, and climate change influence becomes more pronounced in dry seasons from September to December. Cascade development has an effect on runoff of lower reach only in dry seasons due to the limited regulation capacity of reservoirs, and climate changes have an effect on runoff in wet seasons. Climate changes have a less significant effect on fish habitat quality in middle reach than damming, but a more significant effect in lower reach. In addition, the effect of climate changes on fish habitat quality in lower reach is high in dry seasons but low in flood seasons.

An analytical approach to separate climate and human contributions to basin streamflow variability

Climate variability and anthropogenic regulations are two interwoven factors in the ecohydrologic system across large basins. Understanding the roles that these two factors play under various hydrologic conditions is of great significance for basin hydrology and sustainable water utilization. In this study, we present an analytical approach based on coupling water balance method and Budyko hypothesis to derive effectiveness coefficients (ECs) of climate change, as a way to disentangle contributions of it and human activities to the variability of river discharges under different hydro-transitional situations. The climate dominated streamflow change (ΔQc) by EC approach was compared with those deduced by the elasticity method and sensitivity index. The results suggest that the EC approach is valid and applicable for hydrologic study at large basin scale. Analyses of various scenarios revealed that contributions of climate change and human activities to river discharge variation differed among the regions of the study area. Over the past several decades, climate change dominated hydro-transitions from dry to wet, while human activities played key roles in the reduction of streamflow during wet to dry periods. Remarkable decline of discharge in upstream was mainly due to human interventions, although climate contributed more to runoff increasing during dry periods in the semi-arid downstream. Induced effectiveness on streamflow changes indicated a contribution ratio of 49% for climate and 51% for human activities at the basin scale from 1956 to 2015. The mathematic derivation based simple approach, together with the case example of temporal segmentation and spatial zoning, could help people understand variation of river discharge with more details at a large basin scale under the background of climate change and human regulations.

Water Balance Dynamics during Ten Years of Ecological Development at Chicken Creek Catchment

Core Ideas Water balance was calculated for the constructed catchment Chicken Creek. Influence of abiotic and biotic factors feedback mechanisms on the hydrology was determined. Different phases were derived during the development of the ecohydrological system. Difficulties in quantitatively closing the water balance of catchments arise when upscaling point measurements and from insufficient knowledge of the physical boundaries, inner structure, and storage volumes of natural catchments. In addition, there is a strong need for generalizing the relationship between catchment characteristics and hydrological response. Therefore, experimental catchments with well‐known boundaries and conditions could contribute valuable data to hydrological and critical zone research. One of the most well‐established and largest constructed catchments is the Chicken Creek catchment (6 ha including a pond, Brandenburg, Germany) representing an initial ecosystem undergoing highly dynamic ecological development starting from clearly defined starting conditions. Directly after completion of the construction, extensive monitoring equipment was installed to track the ecosystem development and to capture the spatiotemporal variability of meteorological, hydrological, ecological, and soil conditions and vegetation succession. In this study, we focused on the water balance dynamics of the Chicken Creek catchment for the period 2005 to 2015 as influenced by ecological development. Water storage in the catchment was calculated from a three‐dimensional model of groundwater volumes, soil moisture measurements, and water level recordings of the pond. The catchment water balance equation was resolved for evapotranspiration, the only part that was not measured directly. Time series of meteorological, hydrological, and ecological data for 10 yr enabled us to characterize the transient development of the catchment and to evaluate the effect of different feedback mechanisms on catchment hydrology.

Temporal Information Partitioning Networks (TIPNets): A process network approach to infer ecohydrologic shifts

AbstractIn an ecohydrologic system, components of atmospheric, vegetation, and root‐soil subsystems participate in forcing and feedback interactions at varying time scales and intensities. The structure of this network of complex interactions varies in terms of connectivity, strength, and time scale due to perturbations or changing conditions such as rainfall, drought, or land use. However, characterization of these interactions is difficult due to multivariate and weak dependencies in the presence of noise, nonlinearities, and limited data. We introduce a framework for Temporal Information Partitioning Networks (TIPNets), in which time‐series variables are viewed as nodes, and lagged multivariate mutual information measures are links. These links are partitioned into synergistic, unique, and redundant information components, where synergy is information provided only jointly, unique information is only provided by a single source, and redundancy is overlapping information. We construct TIPNets from 1 min weather station data over several hour time windows. From a comparison of dry, wet, and rainy conditions, we find that information strengths increase when solar radiation and surface moisture are present, and surface moisture and wind variability are redundant and synergistic influences, respectively. Over a growing season, network trends reveal patterns that vary with vegetation and rainfall patterns. The framework presented here enables us to interpret process connectivity in a multivariate context, which can lead to better inference of behavioral shifts due to perturbations in ecohydrologic systems. This work contributes to more holistic characterizations of system behavior, and can benefit a wide variety of studies of complex systems.

Temporal information partitioning: Characterizing synergy, uniqueness, and redundancy in interacting environmental variables

AbstractInformation theoretic measures can be used to identify nonlinear interactions between source and target variables through reductions in uncertainty. In information partitioning, multivariate mutual information is decomposed into synergistic, unique, and redundant components. Synergy is information shared only when sources influence a target together, uniqueness is information only provided by one source, and redundancy is overlapping shared information from multiple sources. While this partitioning has been applied to provide insights into complex dependencies, several proposed partitioning methods overestimate redundant information and omit a component of unique information because they do not account for source dependencies. Additionally, information partitioning has only been applied to time‐series data in a limited context, using basic pdf estimation techniques or a Gaussian assumption. We develop a Rescaled Redundancy measure (Rs) to solve the source dependency issue, and present Gaussian, autoregressive, and chaotic test cases to demonstrate its advantages over existing techniques in the presence of noise, various source correlations, and different types of interactions. This study constitutes the first rigorous application of information partitioning to environmental time‐series data, and addresses how noise, pdf estimation technique, or source dependencies can influence detected measures. We illustrate how our techniques can unravel the complex nature of forcing and feedback within an ecohydrologic system with an application to 1 min environmental signals of air temperature, relative humidity, and windspeed. The methods presented here are applicable to the study of a broad range of complex systems composed of interacting variables.

Quantitative Assessment of Hydrological Alteration Caused by Irrigation Projects in the Tarim River basin, China

The Tarim River is the longest inland river at an arid area in China. Deterioration in its ecohydrological system has received much attention world widely. This study presents quantitative assessment of hydrological alterations in the hydrological regime of the Tarim River caused by reservoir irrigation and channel irrigation over a period of over a half century. The improved indicators of hydrologic alteration and range of variability approach were applied to the daily flow rates at the two representative hydrological stations. Our study shows that the annual extreme water conditions (1-, 3-, 7-day annual minimum and extreme low timing) have been altered, compared with the pre-impact period. The average flow rate in July, the 30-day annual maximum flow rates, the date for the maximum rate, the rise rate, and the fall rate show a significant decreasing trend. The improved overall degree of hydrological alteration for the two stations are approximately 68.7% and 61.8%, suggesting a high degree of alteration. This study greatly improved our understanding of impacts of irrigations on the ecohydrological characteristics in the Tarim River.