Hydrologic Subsystems Research Articles

High-Performance Forecasting of Spring Flood in Mountain River Basins with Complex Landscape Structure

We propose the methodology of building the process-driven models for medium-term forecasting of spring floods (including catastrophic ones) in the mountainous areas, the hydrological analysis of which is usually much more complicated in contrast to plains. Our methodology is based on system analytical modeling of complex hydrological processes in 34 river basins of the Altai-Sayan mountain country. Consideration of 13 types of landscapes as autonomous hydrological subsystems influencing rivers’ runoff (1951–2020) allowed us to develop the universal predictive model for the most dangerous April monthly runoff (with ice motion), which is applicable to any river basin. The input factors of the model are the average monthly air temperature and monthly precipitation for the current autumn–winter period, as well as the data on the basin landscape structure and relief calculated by GIS tools. The established universal dependences of hydrological runoffs on meteorological factors are quite complex and formed under influence of solar radiation and physical–hydrological patterns of melting snow cover, moistening, freezing, and thawing of soils. The model shows the greatest sensitivity of April floods to the landscape composition of river basins (49% of common flood variance), then to autumn precipitation (9%), winter precipitation (3%), and finally, to winter air temperature (0.7%). When it is applied to individual river basins, the forecast quality is very good, with the Nesh–Sutcliffe coefficient NSE = 0.77. In terms of the accuracy of process-driven predictive hydrological models for the mountainous areas, the designed model demonstrates high-class performance.

Spatial and Temporal Global Patterns of Drought Propagation

Drought is the most expensive natural hazard and one of the deadliest. While drought propagation through standardised indices has been extensively studied at the regional scale, global scale drought propagation, and particularly quantifying the space and time variability, is still a challenging task. Quantifying the space time variability is crucial to understand how droughts have changed globally in order to cope with their impacts. In particular, better understanding of the propagation of drought through the climate, vegetation and hydrological subsystems can improve decision making and preparedness. This study maps spatial temporal drought propagation through different subsystems at the global scale over the last decades. The standardised precipitation index (SPI) based on the gamma distribution, the standardised precipitation evapotranspiration index (SPEI) based on the log-logistic distribution, the standardised vegetation index (SVI) based on z-scores, and the standardised runoff index (SRI) based on empirical runoff probabilities were quantified. Additionally, drought characteristics, including duration, severity and intensity were estimated. Propagation combined the delay in response in the subsystems using drought characteristics, and trends in time were analysed. All these were calculated at 0.05 to 0.25 arc degree pixels. In general, drought propagates rapidly to the response in runoff and streamflow, and a with longer delay in the vegetation. However, this response varies spatially across the globe and depending on the observation scale, and amplifies progressively in duration and severity across large regions from the meteorological to the agricultural/ecological and hydrologic subsystems, while attenuating in intensity. Significant differences exist between major Köppen climate groups in drought characteristics and propagation. Patterns show intensification of drought severity and propagation affecting vegetation and hydrology in regions of southern South America, Australia, and South West Africa.

Species composition and abundance of free-living turbellarians in three different wetlands in Southern Brazil

Free-living turbellarians mostly live in marine and freshwater environments, but they have been little considered in ecological studies. The coastal plain in southern Brazil harbors a diverse fauna and flora, but only a few studies have related environmental factors to the abundance, richness, and distribution of turbellarians. Hence, we analyzed the structure of turbellarian communities in floating vegetation in three differently sized limnic environments. We aimed to determine differences in abundance, density, and richness of turbellarians among these habitats in relation to environmental factors. We found 1,225 turbellarians (34 species) distributed among 6 taxa. The most abundant was Tricladida with 49.4% relative abundance; the remaining (Catenulida, Dalytyphloplanida, Macrostomorpha, Kalyptorhynchia, and Prorhynchida) were less abundant. We found no significant differences among population parameters and environments. Small shallow lakes are a potentially rich environment, while water channels are the richest environment. Larger shallow lakes are not very diverse for turbellarians. Similarities regarding turbellarian communities among close limnic systems could be explained by the connectivity of bodies of water that presents similar aquatic macrophytes and hydrological subsystems, while larger shallow lakes have a different community because they have their own contributing basin and could be influenced by other factors.

Water Balance in Urban Areas

Hydrological characteristics of urban area are heavily modified related to the natural catchments. Higher part of paved areas causes faster runoff process, the travel time of rainwater is much shorter, as well as the runoff volume is bigger than in natural areas. Sewer network transports higher storm water volume in shorter time: this causes higher hydraulic load on the sewer network and following CSO. Important role in this process play also anthropogenic influences. These significantly change the water balance in urbanised catchments with addition of new water (and pollution) sources or with water transfers between particular hydrological subsystems (both natural and artificial hydrological subsystems – water supply network, sewer network). Because of these reasons, it is desirable, that these negative influences will be reduced to minimum. The goal is to achieve the hydrologic characteristic of the urban catchments alike the characteristics of the natural catchment. Paper present results of a cause study, expressed in form of a system chart of the water balance. Analysed urban area has very complicated relations between particular subsystems (high exfiltration rate from the water supply network as well as high infiltration rate into the sewer network, interactions with surface and underground water). Hydrological function and impacts of particular system elements will be analysed as well as different possible management scenarios. Important parts of the analysed problems are not economical and financial aspects only, but also technical and environmental aspects regarded from the point of view of the integrated water resources management. Last but not least are also very important technical impacts, which can prevent efficient and safe operation of the water supply and sewer networks.

A Budyko-type model for human water consumption

Budyko-type models in hydrology are simple but efficient descriptions of the vegetation-mediated hydrologic cycle in catchments. Based on hypothesized similarities between vegetation and human water consumption interactions in terms of water demand, constraints, and system functioning as well as catchment processes and outcomes, a corresponding Budyko-type framework is proposed here for human water consumption at the catchment scale. To validate this framework, socioeconomic data (human water consumption and economic and agricultural structure data), as well as hydrometeorological data, for 51 human-impacted catchments located in 10 major river basins in China were assembled. The results demonstrate (1) similar observed patterns to the traditional Budyko curves, with two limits and a monotonous increase shape; (2) the same functional form and mathematical features of the derived Budyko-type equation. Parameters of the new Budyko-type model for human consumption are estimated and analyzed based on the concept of water productivity. This study suggests that the functioning of both social and hydrologic subsystems within catchment systems can be explored within a common conceptual framework, thus providing a unified socio-hydrologic basis for the study of human–water systems.

A Bayesian Method for Water Resources Vulnerability Assessment: A Case Study of the Zhangjiakou Region, North China

Water resources vulnerability (WRV) assessment is an important basis for maintaining water resources security in a basin. In this paper, considering the complexity of the water resources system and the uncertainty of the assessment information, a method based on the Bayesian theory was developed for performing WRV assessments while using the constructed indicator system. This system includes four subsystems, the hydrological subsystem, the socioeconomic subsystem, the ecoenvironmental subsystem and the hydraulic engineering subsystem. The WRV degree for each subsystem and the integrated water resources system were assessed. Finally, the assessment results and the characteristics of the Bayesian method were compared with those of the grey relational analysis method and the parametric-system method. The results showed the following. (1) The WRV of the integrated water resources system of the entire Zhangjiakou region was very high; Zhangjiakou City and Xuanhua County have tendencies to belong to Extreme WRV, with probabilities of 26.8% and 25%, respectively, while the other seven administrative counties have tendencies to belong to High WRV, with probabilities ranging from 24.6% to 27%. (2) Compared with the parametric-system method and the grey relational analysis method, the Bayesian method is simple and can effectively address the uncertainty issues with the reliable WRV assessment results.

Water Resources Vulnerability Assessment based on the Parametric-system Method: a Case Study of the Zhangjiakou Region of Guanting Reservoir Basin, North China

Abstract A water resources vulnerability (WRV) assessment is important to maintain water resources safety in a basin. In this paper, an index system, including four subsystems -- the hydrological subsystem, the socioeconomic subsystem, the eco-environment subsystem and the hydraulic engineering subsystem, is constructed for an integrated WRV assessment of the Zhangjiakou region of the Guanting Reservoir Basin, North China. The parametric-system (PS) method based on background value is used for the quantitative WRV assessment of each subsystem and of the integrated water resources system. The results of the calculations show that the degree of vulnerability of Guanting Reservoir Basin is quite serious, with Zhangjiakou City being extremely vulnerable, and Yanqing County and Zhuolu County mildly vulnerable. The assessment process and results, as well as the characteristics of the method used, have been compared with those of the fuzzy optimization (FO) method and the grey relational analysis (GRA) method. The parametric-system (PS) method is appropriate for level classification and rank analysis of many samples in the system, with the obvious advantage of employing the simple process of linear calculation for both the assessment and reference systems. In practical calculation, multiple methods should be used comprehensively, so as to provide a more rational decision-making basis for water resources management.

Temporal patterns of phytoplankton assemblages, size spectra and diversity during the wane of aPhaeocystis globosaspring bloom in hydrologically contrasted coastal waters

The space–time dynamic of phytoplankton diversity and succession was investigated during the wane of aPhaeocystis globosaspring bloom in four distinct hydrological sub-systems of the eastern English Channel. Nutrients, chlorophyll-a concentrations, and phytoplankton composition, standing stocks, size spectra and diversity were monitored during three key periods in 2003: late spring, early summer and summer. Two consecutive diatom assemblages were observed, respectively dominated by: (i) small colonial species (<100 μm;Melosirasp.,Diploneissp. andNavicula transitans) in April; and (ii) large fine-walled cells (>200 μm;Guinardia striataandRhizosolenia imbricata) in May and July. This shift in diatom composition appeared to be related to the potentially limitating silicic acid in early summer. Specific phytoplankton assemblages identified in distinct water masses have evolved from a mature/senescent community towards a relatively homogeneous aestival structure of dominant species that might have been triggered by the wane of theP. globosabloom. Our results also identified a strong heterogeneity in the distribution of secondary species between distinct water masses during the summer period, suggesting that the magnitude of the observed patterns was intrinsically related to the hydrological properties prevailing in each sub-system. The identification of distinct temporal patterns in phytoplankton species diversity and succession following the wane of a spring bloom at relatively small spatial scales (i.e. <10 km) is discussed in the framework ofP. globosablooms in particular and phytoplankton blooms in general and is suggested to have potentially strong consequences on food web dynamics and the carbon cycle in coastal ecosystems.

Poyang Hu (Jiangxi Province, P. R. of China) Area Variations between January 2004 and June 2006 Using ENVISAT Low and Medium Resolution Time Series

Poyang Hu, one of the most regularly flooded areas in China, can be considered as a key hydrological element in flood control and reduction within the middle Changjiang basin. This area was selected as a major test site of the Flood DRAGON Project, part of the MOST-ESA DRAGON Programme. Over two and half years, water extent was monitored based on sixty-four ENVISAT low and medium resolution ASAR and MERIS FR images. It's the first time that such an amount of ENVISAT data was used in monitoring inland lake water extent variations. This original integration approach involves: lake surface variation analysis, yearly submersion time estimation, and a spatial recognition of three major hydrological sub-systems. The results highlight the great potential of ENVISAT, and more largely Earth Observation Medium Resolution data, for large inland water body monitoring and management. This approach can be applied worldwide in the context of global climate change.

Using Stable Water Isotopes to Evaluate Basin-Scale Simulations of Surface Water Budgets

Two rare but naturally occurring isotopes of water, 1H2 18 O and 1H2H16O, are becoming of practical use in diagnosis of climate and earth system model performance. Their value as tracers and validation tools in hydrological subsystems derives from the systematic and different (from each other and from the most abundant water isotope: 1H1H16O) paths and residence times they exhibit as a result of phase change, chemical exchange, and diffusive differentiation. Applications of the simulation of stable isotopic behavior to resolving uncertainty in global climate or earth system models, including river isotopic characterization of basin changes and plantrespired oxygen isotope ‘‘tagging,’’ are limited until more basic criteria such as conservation, current mean climate, and capture of observed variability are demonstrated. Here the authors assess the simulation of isotopic fluxes in basin-scale hydrology, focusing on the representation of land surfaces in numerical models as the current mechanism for incorporating water isotopes. They find that surface water budgets are still rather poorly simulated and inadequately constrained at the scale of large basins, yet surface energy partition can be apparently well captured by models with inadequate land surface parameterization. Despite this, simulations of fluxes and reservoirs of the isotopes H 2 18 O and 1H2H16O are demonstrated here to have diagnostic utility in evaluating surface energy and water budgets. The hypothesis that aspects of basin water budgets and fluxes are explained and improved by isotopic investigation is demonstrated.

Ra isotopes and Rn in brines and ground waters of the Jordan-Dead Sea Rift Valley: enrichment, retardation, and mixing

Thirty-six springs and wells from the Dead Sea Rift Valley were periodically sampled and analyzed. The latter included full chemical analyses, 222Rn and 226Ra (by α-counting emanometry), as well as 228Ra/ 226Ra and 224Ra/ 228Ra activity ratios (γ spectrometry). Sampling stretched over almost 2 yr. Several hundred Rn-Ra analyses and close to a hundred isotopic ratios were measured. Most waters in the Rift Valley have both elevated Ra (several to 750 dpm/L) and Rn (a few hundred to almost 60,000 dpm/L) content. In practically all samples 222Rn activity considerably exceeds that of its parent 226Ra. The Ra content is the result of all Dead Sea Rift Valley waters being mixtures of fresh water with saline brines. Ra is efficiently extracted from surrounding rocks into the brine end member. 228Ra/ 226Ra ratios are exceptionally low −0.07 to 0.9, mostly less than 0.2. This apparently reflects the U over Th enrichment in the source rocks that contribute the Ra. Ra enrichment (both 228Ra and 226Ra) is locally correlated throughout the Rift Valley with water salinity. This correlation can be used to constrain the age of the brine-freshwater mixing process. In one of the hydrologic subsystems studied (the Fuliya block), the mixing of the shallow ground water must have occurred in less than 200 to 300 yr ago, probably before no more than some 30 yr. High radon activities in surface waters along the Dead Sea Rift Valley result from the formation of radium-enriched linings on the aquifer rock surface. The mixing of the radium-extracting brines with fresh water leads to continual adsorption of radium as water salinity decreases. The unique combination of fast upward flow and continual mixing in the Dead Sea Rift Valley accounts for a constant replenishment of radium in the waters. This causes a gradual buildup of a radium lining on the aquifer walls until eventually a steady-state surface activity is established.

The water environs of Okefenokee swamp: An application of static linear environ analysis

A static water budget model is constructed for the Okefenokee Swamp watershed (swamp plus upland portions) and decomposed into partition units called environs. Flow, storage, intercompartmental transfer and residence time analyses of these units are performed by environ analysis to determine qualitative and quantitative characteristics of Okefenokee ecosystem hydrology. The analysis indicates two relatively discrete hydrologic subsystems within the watershed. One consists of swamp surface water, driven by precipitation over the swamp. The other consists of upland sirface water plus subsurface water in both swamp and uplands, whose source is precipitation on the uplands. Little exchange occurs between these two subsystems.

Definition hydrologic units for water studies in Arkansas

Water studies that use cause‐effect models are planned for Arkansas. Cause‐effect models that incorporate the physical and flow characteristics of the hydrologic system in the state can serve as tools to predict the effects of various stresses on the system. Another very important use of models is to evaluate the adequacy of the data networks in meeting the data needs of the state. Arkansas is divided into several flow subsystems for use as study units. Natural hydrologic boundaries of a stream and of the groundwater flow parts of a system commonly do not coincide. In the coastal plain, the natural aquifer boundaries are taken as the principal boundaries of the hydrologic subsystems, and natural surface water boundaries may enclose an additional peripheral area that must be considered. In the interior highlands, surface water divides are the principal boundaries of the hydrologic subsystems.