查看更多>>摘要：Biological carbon pumps (BCPs) convert dissolved inorganic carbon (DIC) into autochthonous organic carbon (AOC), which is the key to form long-term stable carbonate weathering-related carbon sink. The DIC fertilization may increase the strength of BCP. As a phase of BCP, eutrophication is one of the major problems in surface water environments which shows poor water quality with harmful cyanobacteria blooms. It is generally believed that the controlling elements of eutrophication are nitrogen (N) and phosphorus (P), while the controlling elements of BCP also includes carbon (C). Meanwhile P removal by BCPs through the coprecipitation of P with calcite and Fe (III) oxyhydroxide colloids decreases its content in water bodies and prevent water from cyanobacteria eutrophication. In the present study, we examine the seasonal variations of general physiochemical parameters of the surface water, DIC, total N and total P concentrations, chlorophyll concentrations in three karst river-reservoir systems (PZR, PDR and HFR) in Guizhou Province, Southwest China. The phytoplankton community structure dynamics and the settling flux of the total P and P fractions in the settling particulate matter in PZR and HFR were also examined. It was found that: (1) the nutrient limitations of BCPs shifted from C-limitation to N- or Plimitation after the rivers were dammed; (2) P removal by BCPs reduced the total P concentration and increased the stoichiometric N:P ratio in surface waters; (3) P removal by BCPs alleviated the development of eutrophication by decreasing the relative abundance of Cyanobacteria. Our results demonstrate that the damming of a river may shift the nutrient limitation patterns of dammed karst rivers and the P removal by BCP may retard the development of water body into Cyanophyta-type eutrophication. This may have important implications for eutrophication control (i.e., strengthening BCP effect via DIC fertilization) in HCO3-Ca type surface water, especially in karst areas, which cover about 15% of the world land surface.
查看更多>>摘要：River and floodplains are process-response systems that geomorphic states are typically results of hydrologic drivers and geologic setting. Large sand-bed braided rivers geomorphology shows more sensitive dynamic evolution and significant space-time difference. However, few investigations have been focused on it. Here we show that river characteristics including expansion-contraction and elevation heterogeneity of the river cross sections affect erosion and deposition partially and cause spatially differential variation of morphology in the Yanni Wetland, in the middle of Yarlung Zangbo-Brahmaputra River (YBR), and interannual hydrology process is main responsible for temporal river morphology variation as the different impact of each HIs on river morphology. We found the river morphology varied significantly with main channel shifting and branches removing over the past 35 years. Within HIs, bankfull flow (Q(bf)) is the channel forming discharge equal to 5.6 year flood approximately. The sub-bankfull flow (Q(sf)), and main channel full flow (Q(mf)) are channel maintaining discharge. Affected by the broad width, main channel straighten was a result of years of large floods over Q(bf). Small and moderate floods within the Q(sf) and Q(bf) are also important as the morphology adjustments were mainly observed in sub-channels. And effective discharges with the Nash approach (Q(1/2)) are more suitable in braided river compared with Wolman-Miller approach (Q(ef)). Our research highlighted complexity response of landform and hydrology to river morphological variations in sand-bed braided riverine wetland. It provides reference basis for studying the ecological importance of flood dispatches and complements the scarcity of research data on morphological evolution in Tibet. And a new method for assessing the HIs with remote sensing was established that is convenient with high accuracy and suitable for wide-valley river with multiple channels. We anticipate our method to be a new view to analyze ecological hydrology, and promote better managing river ecosystems.
查看更多>>摘要：Riparian ecosystems fundamentally depend on groundwater, and thus accurate estimates of daily groundwater evapotranspiration rate (ETg) is curial for understanding the interactions between groundwater and vegetation. Up to now, various methods (i.e., White, 1932; Hays, 2003; Soylu et al., 2012) have been proposed to estimate daily ETg using the water table fluctuations. The objective of this paper was to evaluate and compare their performances under various water table conditions in field environments. For this purpose, we employed a variety of measurements (i.e., water table levels, latent heat flux and soil water contents) at a riparian forest (T. ramosissima) in Northwest China in 2017. Our results showed that the White method is suitable for use during the water table declining periods. Also, the selected time intervals could have impacts on the estimations of ETg. The Soylu method and the Hays method performed well under various water table conditions. Thus, it seems that the Hays and Soylu methods are more suitable for long-term ETg estimates in field environments. In addition, the percentage of plant transpired water from groundwater varied during the growing seasons. The riparian plants mainly use soil water during the early growing stages, and it tended to use groundwater during the late growing stages. In the future, more isotope-based studies were needed to verify the seasonal patterns of water uptake of the riparian forest.
查看更多>>摘要：The accuracy of hydrologic and hydrodynamic models, used to study urban hydrology and predict urban flooding, depends on the availability of high-resolution terrain and infrastructure data. Unfortunately, cities often do not have or cannot release complete infrastructure data, and high-resolution terrain data products are not available everywhere. In this study, we quantify how the accuracy and precision of urban hydrologic hydrodynamic models vary as a function of data completeness and model resolution. For this aim, we apply the one-dimensional (1D) and coupled one-and two-dimensional (1D-2D) versions of the U.S. Environmental Protection Agency's Storm Water Management Model (SWMM) in an urban catchment in the city of Phoenix, Arizona. Here, we have collected detailed infrastructure data, a high-resolution 0.3-m LiDAR-based digital elevation model, and catchment properties data. We tested several model configurations assuming different levels of (i) availability of stormwater infrastructure data (ranging from 5% to 75% of attribute-values missing) and (ii) terrain aggregation (i.e., 4.6 m and 9.7 m). These configurations were generated through random Monte Carlo sampling for SWMM 1D and selective sampling with four cases for SWMM 1D-2D. We ran simulations under the 50-year return period design storm and compared simulated flood metrics assuming the highest resolution and complete data model configuration as a reference. The study found that the model may over or underestimate flood volume and duration with different levels of missing data depending on the parameters - roughness, diameter or depth, and that model performance is more sensitive to missing data that is downstream and closer to the outfall as opposed to missing data upstream. Errors in flood depth, area and volume estimation are functions of both the data completeness and model resolution. Missing feature data leads to overestimation of flood depth, while lower model resolution results in underestimating flood depth and overestimating flood extent and volume.
查看更多>>摘要：Direct flood damage is commonly assessed using damage models (i.e., vulnerability functions and fragility curves), which describe the relationship between hazard, vulnerability, and the (probability of) damage for items exposed to floods. In this paper, we introduce a non-dimensional impact parameter that, according to the physics of damage mechanisms and/or tuned on field or lab data, combines water depth and flow velocity in a general and flexible form. We then suggest a general approach to assess relative damage functions for items of different nature, subject to either progressive or on-off damage processes. The proposed method enhances traditional tools that use inundation depth as the main (or only) explicative variable, and allows recasting the results from previous studies in an elegant, flexible and unique form. Compared to multivariate models that link flow variables to damage directly, the physics-based approach allows for an intelligible assessment of flood hazard and the associated damage, even in case of scarce or sparse data. The proposed impact parameter and the related procedure to assess the relative damage functions are applied to different kinds of exposed items (people, vehicles, and buildings), demonstrating the general applicability and validity of the proposed method.
查看更多>>摘要：Generally, reliable simulation results are obtained by calibrating and validating the parameters of a hydrological model through a split-sample test. To obtain adequate and stable calibration and validation results of a hydrological model, calibration data with sufficient length should be used; therefore, a study on the estimation of appropriate calibration data length is required. In this study, the appropriate calibration data length was estimated for three hydrological models (GR4J, IHACRES, and Sacramento models) with varying complexities using the Sobol global sensitivity analysis method. As a result of analyzing the appropriate calibration data length in three hydrological models for three dam catchments in Korea, a relatively stable simulation result could be derived using more than eight years of calibration data length. In addition, it was confirmed that the appropriate length of the calibration data increased as the size of the catchment decreased. In the case of the Sacramento model with the largest number of parameters, the variability of the optimum parameter values was high, even if the calibration period increased. Therefore, the variability size of the optimum parameter values is an improper scale for estimating the appropriate calibration data length when many parameter uncertainties exist. However, as a result of analyzing the parameter sensitivity of the Sacramento model, the variability of the parameter sensitivity decreased as the calibration period increased. The variability of model performance was also related to the variability of parameter sensitivity rather than to the variability of optimal parameter values. Therefore, parameter sensitivity analysis can be used to estimate the calibration data length for various hydrological models, including hydrological models with high uncertainty.
查看更多>>摘要：How to rationally optimize the allocation of surface water and groundwater resources in saline-alkali areas is a difficult problem in current model optimization. Based on an interval two-stage stochastic programming (ITSP) method, this paper considers the system risk involved in saline-alkali land treatment, follows a robust optimization method, and constructs an interval two-stage data-driven subrobust optimization (ITDRO) model, which can optimize the distribution of groundwater and surface water for different crops and realize the combination of wells and canals through the joint dispatch of surface water and groundwater. This paper takes the Urad Irrigation Area as the research object, and the obtained results provide water distribution objectives under situations of multiple sources of water, multiple crops, and different robust coefficients. After the successful calibration and verification of the SaltMod model, the water distribution target is taken as the main input parameter and substituted into the simulation model based on the principle of water and salt balance. The output includes soil salinity, drainage salinity, groundwater salinity (GWS), groundwater table (GWT) depth, and drainage. The results show that the integrated ITDRO and SaltMod model can control the groundwater level below the critical depth under the premise of satisfying crop irrigation, reducing the groundwater level by approximately 0.75 m and the GWS in the irrigation area by approximately 0.68 g/L, which can provide a reference for the prevention and control of soil salinization and waterlogging. This approach is suitable for arid and semiarid regions that face similar problems.
Adamowski, Jan F.Wen, XiaohuYin, ZhenliangYang, Linshan...
13页
查看更多>>摘要：Actual evapotranspiration (ETa) has significantly increased under recent climate and vegetation changes. Discriminating the primary driver of ETa variation would improve our knowledge of the interaction between regional hydrological and ecological systems. In this study, a reliable ETa dataset was obtained by validating three ETa products from different sources with in-situ observations. We modified the elasticity-coefficient method using partial correlation, and compared it with the traditional regression-based method in estimating ETa variation in northwest China (NWC). On the basis of the magnitude and the sensitivity of ETa variation, results revealed that annual ETa significantly increased (2.32 mm/yr, p <= 0.05) in NWC over 1982-2015 with over 75% of the vegetated area showing an increasing trend. Robust in capturing spatial variation patterns in ETa the partial correlation coefficient-based elasticity method was able to explain 83% of the annual variation in ETa. Precipitation, temperature, and NDVI were the most important factors controlling the increase in annual ETa from 1982 to 2015. Regionally, precipitation was the dominant factor and contributed 73% to the variation of annual ETa in the vegetated NWC. However, the contribution rates of precipitation varied across the different land cover types and ranged from 31% in irrigated cropland to 81% in the steppe. Potential uncertainty in the attribution of causative factors could arise in selecting the separation method and potential driving factors. Establishing a reliable relationship between ETa and potential driving factors should be confirmed with observations. The present study's results can guide sustainable water resources management and ecological restoration in water limited regions.
Dawkins, Laura C.Osborne, Joe M.Economou, TheodorosDarch, Geoff J. C....
26页
查看更多>>摘要：Synthetic rainfall simulations from stochastic models are commonly used for water resource management, as they are able to provide a wider range of meteorological conditions than those seen in the observed record. Here, we present a novel stochastic rainfall modelling framework, the Advanced Meteorology Explorer (AME), which combines and extends existing methods to enhance model flexibility, and meet a number of key water industry needs. This framework allows for the simulation of physically consistent synthetic daily rainfall data, coherently in space and time, on a high-resolution grid over a region of interest. The AME uses an advanced hidden Markov model structure within a Bayesian hierarchical framework to represent daily rainfall at a set of locations in a region, conditional on important climate drivers. The climate drivers included in the rainfall model at each location are able to vary using penalised regression, ensuring a transferable model that can be applied to different locations without adaptation. The dependence between locations is modelled following a flexible copula approach, able to capture varying dependence structures within the data, allowing for spatially coherent simulations at the modelled locations. Simulations are then interpolated to a high-resolution grid using a terrain adjusted inverse-distance weighted interpolation method. The AME framework is applied to 105 years (1914-2018) of daily rainfall data at 39 sites in the Greater Anglian region of the UK, and used to generate 1000 alternative realisations of the same period on a 5 km grid over the region. Validation of these simulations shows how the AME framework is able to accurately capture rainfall occurrence and intensity, as well as long-duration meteorological drought behaviour, important for quantifying water resource risk in this dry region. This framework has the potential to be applied to other regions, incorporate additional weather variables and the effect of climate change, and the resulting simulations can be used for environmental risk assessment in any industry impacted by rainfall.
查看更多>>摘要：Spontaneous imbibition (SI) of wetting fluids is an important process for many hydrological and geological applications. In this study, we investigated experimentally and theoretically the SI process in a dual-porosity medium consisting of the matrix and the filled fracture. Low-field nuclear magnetic resonance (LF NMR) technology was used to dynamically monitor the distribution of the imbibed water in the dual-porosity media during the SI experiments. Based on the LF NMR theory, a cut-off method was proposed to quantitatively distinguish the imbibed water from the matrix and the filled fracture. The results showed that the rate of matrix imbibition was greater in the dual-porosity media than in single-porosity media. This inconsistent rate of matrix imbibition between the single-porosity media and the dual-porosity media was caused by the enhanced mass transfer between the matrix and the filled fracture. An analytical model was then proposed to characterize this enhanced mass transfer between the matrix and the filled fracture. It was found that the rate of matrix imbibition was not only affected by the presence of the filled fractures but also depended on the size of the particles filled in the fracture. A clear non-monotonic relationship was found between the rate of matrix imbibition and the size of the particles filled in the fracture. The rate of matrix imbibition initially increased and then decreased as the size of the particles filled in the fracture increased. The proposed analytical model not only highlighted the mechanism of enhanced mass transfer between the matrix and the filled fracture, but was also able to determine the optimum equivalent capillary diameter of the filled particles in the fracture for enhanced rate of matrix imbibition in dualporosity media.
NSTL
Elsevier