Hydrological Status Research Articles

Climatic and hydrological variations on the southwestern Tibetan Plateau during the last 30,000 years inferred from a sediment core of Lake Zabuye

Climate change on the Tibetan Plateau (TP) is governed by the mid-latitude westerlies and Indian summer monsoon (ISM). However, the past hydrological changes on the TP induced by interactions between the westerlies and the ISM remain unclear. A sediment core from Lake Zabuye on the southwestern TP was analyzed to reconstruct climatic and hydrological variability over the last 30 kyr. Stable isotopic compositions (δ13C and δ18O) of authigenic carbonate act as an indicator of hydrological status for closed-basin lakes on the TP. Four major climatic and hydrological stages were identified: (1) last glacial maximum (29.8–18.9 cal kyr BP), the influence of the westerlies dominated, and a cold-wet climate prevailed; (2) last deglaciation (18.9–11.8 cal kyr BP), the influence of the westerlies receded, and a general trend of decreased wetness was interrupted by two pronounced glacial meltwater events recorded at 17.2 and 15.2 cal kyr BP, respectively; (3) early and middle Holocene (11.8–3.8 cal kyr BP), the Holocene climate optimum was attained and sustained under the dominance of ISM circulation; (4) late Holocene (from 3.8 cal kyr BP to the present), the ISM collapsed during the middle to late Holocene, and a hypersaline lacustrine environment was ultimately formed, as inferred from mirabilite deposition and isotopic signals. Our lake record demonstrates an anti-phase relationships between the westerlies and the ISM on the glacial-interglacial timescale over the southwestern TP. We suggest that both North Atlantic climate and tropical ocean temperature are major drivers of climatic variations on the TP.

Dynamic High Resolution Hydrological Status Monitoring in Real-Time: The UK Water Resources Portal

Understanding the current hydro-meteorological situation is critical to manage extreme events and water resources. The United Kingdom Water Resources Portal (UKWRP) has been developed to enable dynamic, interactive access to hydro-meteorological data across the United Kingdom, including catchment daily rainfall (near), real-time daily mean river flows, groundwater levels, real-time soil moisture data, and standardised climate indices. The UKWRP offers a way of exploring the full range of river flow and rainfall variability, including comparing current conditions to those in the past, from droughts to floods. A variety of different plotting capabilities mean users can view and explore data in different ways depending on their requirements. Here we discuss the mechanisms and the engagement undertaken to develop the UKWRP, in addition to the technical issues and solutions of bringing multiple data sources and types together, how the data are processed, stored and published to deliver an integrated tool for water resources management. The UKWRP enables all water users–from farmers, to water companies to members of the general public–to view and explore the data used by regulators to manage water supplies. We demonstrate how the UKWRP can be used to monitor the hydrological situation, using recent examples of both floods and droughts, and enables consistent messaging and universal access to data and information. Finally, we discuss the decisions the information provided in the UKWRP can support, and possible future developments. The UKWRP is aimed at the United Kingdom water research and management community, but we envisage that the Portal (and the development pathway and technical solutions reported here) could provide a useful exemplar for similar systems in other international settings.

Assessment of the hydrological and erosive status of South Andaman’s watersheds using drainage morphometric studies and climatic water balance model

Soil erosion is an inevitable geomorphic process that aids in evaluating and analyzing the erosive and hydrological status of the watershed. The present investigation focuses on the qualitative evaluation of the hydrologic and erosive status of eighteen watersheds (area > 10 km2) of south Andaman using drainage morphometric studies. The objective of the present study was addressed with the aid of GIS and remote techniques. The results suggest that four watersheds such as Burmanallah, Carbyn, Burataga, and Dhania showed low levels of soil erosion. Whereas, seven watersheds via., Putatang, Colinpur, Jirkatang I, Dhanikhari, Jarawa I, Jarawa III, and Tirur exhibited high levels of soil erosion. The rest of the seven watersheds via., Bhagoda, Bilap, Bill, Jirkatang II, Jarawa II, Jarawa IV, and Mannarghat were prone to moderate levels of soil erosion. Further, the findings from forty years’ time series climate-water balance modelling reaffirm that more than 60% of rainfall divulges into the adjacent seas as surface runoff. Thus, the copious amount of fresh water and loads of nutrient-rich fluvial influx at the shallow depths of coastal frontiers aid the mangrove to respond.

Role of small wetlands on the regime shift of ecological network in a wetlandscape

Globally, wetlands in many places have been at risk by natural and anthropogenic threats including climate change and land use and land cover change. Because of their significant contribution to providing various ecosystem services, understanding the vulnerability to various threats and the effects of their loss on various scales and aspects is an imminent issue for wetland conservation. On a landscape scale, these wetlands can be distributed in a variety of forms (e.g., by size, bathymetry, geology, etc.) and interconnected by dispersal of inhabiting species. Here, we use the network modeling approach associated with wetland hydrology to analyze potential shifts in an ecological network caused by hydro-climatic and anthropogenic forcings. We focus on the role of small wetlands which are often easily ignored in assessing landscape function because of their minor occupancy in an overall area. Specifically, by manipulating the hydrological status of the small wetlands, an area of which only contributes 0.82%, we observed the degrading effects on the characteristics (mean degree and network efficiency) of resulting ecological networks. Our results suggest that wetland size does not necessarily correlate with network centralities, and the loss of small wetlands acting as high centrality nodes induce a critical regime shift in network structure and function. Although hypothetically tested, because of their high sensitivity to hydro-climatic conditions and vulnerability to land use and land change along with climate change effects, the persisting functional loss of small wetlands is highly expected which eventually leads to trapping in the undesirable state of an ecological network. Our study is expected to provide a framework to evaluate the importance of small wetlands that can be easily ignored from an area-based point of view in a landscape.

Electrochemical and Structural Modifications of Humic Acids in Aerobically and Anaerobically Incubated Peat

Exposure to oxygen and aerobic biological activity during drought periods alters the availability of terminal electron acceptors (TEA) in the peat catotelm layer. We investigated the changes in the electrochemical and chemical characteristics of humic acids (HA) induced by subjecting air-dried sphagnum peat to biological oxidation or reduction during a 90-day incubation experiment. Structural modifications of HAs from anaerobically (HAred) and aerobically (HAox) incubated peat were investigated by ATR-FTIR, UV–vis, and EEM fluorescence spectroscopy. Number and strength of acid groups were characterized by titration, while changes in redox properties were characterized by cyclic voltammetry and quantified by coulometry with mediated electrochemical oxidation (MEO). Exposure to oxygen had small effects, but compared to anaerobic incubation, decreased by 20% the capacity of HA to reduce the radical ion of 2,2′-Azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS●−), passing from 2.77 ± 0.13 mmole- gHA−1 in HAred to 2.21 ± 0.10 mmole- gHA−1 in HAox. Pseudo-first-order electron transfer kinetic constants were 13.3 ± 1.2 s−1 for HAox and 16.7 ± 1.4 s−1 for HAred. Alterations in the hydrological status of the catotelm have minor effects on the actual in situ availability of organic TEA, but if coupled to intensified biological activity they may result in significant variations of greenhouse gases emissions.

Identification of ecological networks and nodes in Fujian province based on green and blue corridors

China's Green Space System Planning (GSSP) research has gradually expanded from central urban areas to municipal and provincial scales in recent years. Besides, the research on the role of green space in the water environment has also attracted much attention. However, the study of green corridors usually ignored hydrological data, which widespread absence especially in the large area scale. And the scale of green corridor construction mainly focused on central urban areas. This paper took China's Fujian province as an example. Based on the DEM elevation data, the article identified blue corridors without hydrological data. In addition, the green corridors were determined based on the land use data. According to the green corridors and blue corridors protection, we identified the ecological networks and nodes by the network analysis method. The results showed that the blue corridors identified by DEM data were consistent with the hydrological status quo. The regional status of the identified ecological networks and nodes were basically in line with their characteristics, proving the value of the planning methods. Finally, based on the identification results, suggestions for Fujian's ecological networks and nodes are put forward.

Improving Indicators of Hydrological Alteration in Regulated and Complex Water Resources Systems: A Case Study in the Duero River Basin

Assessing the health of hydrological systems is vital for the conservation of river ecosystems. The indicators of hydrologic alteration are among the most widely used parameters. They have been traditionally assessed at the scale of river reaches. However, the use of such indicators at the basin scale is relevant for water resource management since there is an urgent need to meet environmental objectives to mitigate the effects of present and future climatic conditions. This work proposes a methodology to estimate the indicators of hydrological alteration at the basin scale in regulated systems based on simulations with a water allocation model. The methodology is illustrated through a case study in the Iberian Peninsula (the Duero River basin), where different minimum flow scenarios were defined, assessing their effects on both the hydrological alteration and the demand guarantees. The results indicate that it is possible to improve the hydrological status of some subsystems of the basin without affecting the water demand supplies. Thus, the methodology presented in this work will help decision makers to optimize water management while improving the hydrological status of the river basins.

Response of the chironomid community to late Holocene climate change and anthropogenic impacts at Lake Ulungur, arid Central Asia

Lake ecosystems in arid Central Asia are in crisis due to water abstraction and eutrophication, and it is important to understand their response to combined climate and human impacts. In this study, based on the relationship between modern chironomids and salinity, we studied subfossil chironomid remains in a ~4550-year sedimentary record from Lake Ulungur in northwest China, with the aim of reconstructing past ecosystem dynamics, especially in response to climate change and human impacts. The results show that from 4550–580 cal yr BP the hydrological status of Lake Ulungur was transformed from close to open and the salinity decreased causing an increase in freshwater chironomid species. Comparison with regional paleoclimatic records makes us to infer that the lake ecosystem evolution has been primarily controlled by changes in the westerly driven by the Northern Hemisphere insolation. Since 580 cal yr BP, the lake returned to be closed and the structure of the aquatic community reorganized. In recent centuries, human activities have made a more significant effect on lake ecosystems in northwest China than natural climate changes, which largely was induced by a surge in the human population related to national policies. Furthermore, due to the combined effects of global warming and intensifying human activities, lake ecosystems in Central Asia are subject to unprecedented anthropogenic pressures and urgent action is needed to protect them.

Distinct microbial communities alter litter decomposition rates in a fertilized coastal plain wetland

AbstractHuman activities have led to increased deposition of nitrogen (N) and phosphorus (P) into soils. Nutrient enrichment of soils is known to increase plant biomass and rates of microbial litter decomposition. However, interacting effects of hydrologic position and associated changes to soil moisture can constrain microbial activity and lead to unexpected nutrient feedbacks on microbial community structure–function relationships. Examining feedbacks of nutrient enrichment on decomposition rates is essential for predicting microbial contributions to carbon (C) cycling as atmospheric deposition of nutrients persists. This study explored how long‐term nutrient addition and contrasting litter chemical composition influenced soil bacterial community structure and function. We hypothesized that long‐term nutrient enrichment of low fertility soils alters bacterial community structure and leads to higher rates of litter decomposition especially for low C:N litter, but low‐nutrient and dry conditions limit microbial decomposition of high C:N ratio litter. We leveraged a long‐term fertilization experiment to test how nutrient enrichment and hydrologic manipulation (due to ditches) affected decomposition and soil bacterial community structure in a nutrient‐poor coastal plain wetland. We conducted a litter bag experiment and characterized litter‐associated and bulk soil microbiomes using 16S rRNA bacterial sequencing and quantified litter mass losses and soil physicochemical properties. Results revealed that distinct bacterial communities were involved in decomposing higher C:N ratio litter more quickly in fertilized compared to unfertilized soils especially under drier soil conditions, while decomposition rates of lower C:N ratio litter were similar between fertilized and unfertilized plots. Bacterial community structure in part explained litter decomposition rates, and long‐term fertilization and drier hydrologic status affected bacterial diversity and increased decomposition rates. However, community composition associated with high C:N litter was similar in wetter plots with available nitrate detected, regardless of fertilization treatment. This study provides insight into long‐term fertilization effects on soil bacterial diversity and composition, decomposition, and the increased potential for soil C loss as nutrient enrichment and hydrology interact to affect historically low‐nutrient ecosystems.

Recent hydrological status of the Aegean Sea derived from free drifting profilers

Being a semi-enclosed basin of the Mediterranean Sea, the Aegean Sea comprises a complex hydrology that plays a significant role in the hydrology of the Eastern Mediterranean Sea. Its interaction with many sub-basins, along with its contribution towards the formation of deep and intermediate water, makes it an ideal case for the study of hydrological changes in transitional areas. Since 2010, the operational monitoring of the basin has been significantly enriched due to the deployment of autonomous free-drifting profilers (Argo floats) under the framework of the newly formed Greek Argo Research Infrastructure activities. In this study the hydrological status of the area is examined for the period 2010 - 2017 using the temperature and salinity profiles acquired from Argo floats that operated in the basin. The profiles are analyzed together with complementary remote sensing and model outputs datasets in order to present the spatio-temporal distribution of the co-existent water masses and shed light on hydrological features and changes that took place throughout the basin in an attempt to reassess its hydrological status during the last decade. The distribution of the physical properties in different sub-regions and their interaction is examined reconstructing a general picture of strong latitudinal gradients in the T-S and σθ fields from the upper layers towards the deeper zones. Interannually, findings indicate changes of the Aegean water masses structure within the water-column. Deep homogenization in the upper layers is recorded mainly during the winter periods of 2011-2012, 2014-2015 and 2016-2017 in the southern, central, and northern parts of the area accordingly. The observed dense water formation events, along with mixing and advection appear to alterate the water column physical properties structure and affect the dynamics of the surface and sub-surface dominant water masses in the Aegean. The results further highlight the valuable information that can be extracted from the operation of free-drifting profilers in enclosed marginal seas similar to the Aegean case.

Alteration of the Ecohydrological Status of the Intermittent Flow Rivers and Ephemeral Streams due to the Climate Change Impact (Case Study: Tsiknias River)

Climate change projections predict the increase of no-rain periods and storm intensity resulting in high hydrologic alteration of the Mediterranean rivers. Intermittent flow Rivers and Ephemeral Streams (IRES) are particularly vulnerable to spatiotemporal variation of climate variables, land use changes and other anthropogenic factors. In this work, the impact of climate change on the aquatic state of IRES is assessed by the combination of the hydrological model Soil and Water Assessment Tool (SWAT) and the Temporary Rivers Ecological and Hydrological Status (TREHS) tool under two different Representative Concentration Pathways (RCP 4.5 and RCP 8.5) using CORDEX model simulations. A significant decrease of 20–40% of the annual flow of the examined river (Tsiknias River, Greece) is predicted during the next 100 years with an increase in the frequency of extreme flood events as captured with almost all Regional Climate Models (RCMs) simulations. The occurrence patterns of hyporheic and edaphic aquatic states show a temporal extension of these states through the whole year due to the elongation of the dry period. A shift to the Intermittent-Pools regime type shows dominance according to numerous climate change scenarios, harming, as a consequence, both the ecological system and the social-economic one.

滨海湿地生态系统土壤微生物及其影响因素研究综述

PDF HTML阅读 XML下载 导出引用 引用提醒 滨海湿地生态系统土壤微生物及其影响因素研究综述 DOI: 10.5846/stxb201909201961 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41230751）；自然资源部公益性行业科研专项（201511086）；浙江省自然科学基金项目（LY19D010007）；自然资源部海岸带开发与保护重点实验室开放课题（2019CZEPK09） Progress and prospect of soil microorganisms and their influencing factors in coastal wetland ecosystem Author: Affiliation: Fund Project: [Foundation: National Natural Science Foundation of China (41230751); Special Funds for Public Industry Research Projects of the Ministry of Natural Resources(201511086); Natural Science Foundation of Zhejiang Province (LY19D010007)] 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:土壤微生物是滨海湿地生态系统中不可或缺的关键组分，在土壤发育、物质循环和污染物净化等诸多土壤生态过程中发挥着重要作用，对滨海湿地生态系统的维持与健康具有重大影响。系统梳理了滨海湿地土壤微生物群落结构特征和多样性，综述了土壤理化性质、植被状况、水文因素、生物入侵、全球变化、湿地开垦、石油污染等因素对滨海湿地土壤微生物的影响。在此基础上，对今后的研究重点提出了4个方面的展望：①加强全球变化多因子交互作用下滨海湿地土壤微生物的响应机制；②强化滨海湿地土壤微生物与环境因子的互作机理；③深化滨海湿地水动力条件对土壤微生物的影响机制；④开展土壤微生物与滨海湿地生态系统物质循环综合研究。研究以期为滨海湿地生态系统的保护和修复提供参考。 Abstract:As an indispensable component in coastal wetland ecosystem, soil microorganisms play an important role in many soil ecological processes, such as soil development, material circulation and pollutant purification, and have a significant impact on the maintenance and health of coastal wetland ecosystems. In this paper, the structure and diversity of soil microbial community in coastal wetlands were systematically reviewed, and the effect of influencing factors such as soil physicochemical properties, vegetation status, hydrological status, biological invasion, global change, wetland reclamation, and oil pollution on soil microorganisms in coastal wetlands were summarized. On this basis, four perspectives are proposed for the future research: 1) strengthening the response mechanism of soil microorganisms in coastal wetland under the interaction of multiple factors of global change; 2) strengthening the interaction mechanism of soil microorganisms and environmental factors in coastal wetland; 3) deepening the influence mechanism of hydrodynamic conditions on soil microorganisms in coastal wetland; and 4) carrying out the comprehensive research on soil microorganisms and material circulation of coastal wetland ecosystem. This study is expected to provide reference for the protection and restoration of coastal wetland ecosystems. 参考文献 相似文献 引证文献

Environmental factors shaping assemblages of ostracods (Crustacea: Ostracoda) in springs situated in the River Krąpiel valley (NW Poland)

We investigated the ostracod assemblage structure in springs of a small lowland River Krąpiel valley. Environmental factors and the potential of ostracods as indicators of spring type were analysed. The analysis involved the type of spring, substrate, physicochemical parameters, and the river valley's hydrological status as environmental factors. A total of thirty ostracod species were recorded. The average count of ostracod individuals in a sample amounted to 100. The assemblages were dominated by juvenile Candona sp., juvenile Psychrodromus sp., Cypria ophtalmica, and Cypridopsis vidua. The spring species accounted for less than 1% of the individual counts, except for juvenile Psychrodromus sp. with 21% and Eucypris pigra with 4%. The average number of taxa per spring was 5. The ostracod assemblages were significantly influenced by limnocrene springs, spring flooding by the river overflow, the presence of coarse leaf litter, the presence of fine organic matter, a high content of NH4 as well as by BOD5, conductivity, pH, Fe, the river habitat modification index (RHM), the habitat modification score (HMS), and the river habitat quality (RHQ). The habitat conditions for the spring species appeared to be enhanced by the domination of mineral substrate over fine particulate organic matter, an elevated pH, the presence of leaf-derived organic matter, and the absence of flooding by the river. The spring species showed no association with the Krąpiel valley hydrological factors.

Effect of land use land cover changes on runoff using hydrological model: a case study in Hiranyakeshi watershed

The assessment of the effects of land use land cover changes is crucial to know the hydrological status of the river basins. Various applications like remote sensing, geographic information system (GIS), and hydrological modeling approach are required to visualize and understand these effects on the watershed hydrological system. The research focuses on assessing the effects of land use land cover (LU/LC) changes and its impacts on the runoff in the Hiranyakeshi watershed using a semi-distributed hydrological model viz. soil and water assessment tool (SWAT). Therefore, this research was initially carried out by analyzing changes in LULC by classifying Landsat 7 and Landsat 8 satellite images for the year 2000 and 2015. The LULC classification is prepared with different classes such as forest, agriculture, fallow land, plantation, water bodies, and urban area. The accuracy assessment of the classified images was performed by error matrix; the values were found to be 65% (for two classified images); the kappa coefficient value found to be 0.51 and 0.56 for the year 2000 and 2015. The classification results obtained are within satisfactory limits; hence, the classified image is used to assess the changes in LULC over the period. Results show an increase in agricultural activities (11.45%), urban area (1.15%), water body (0.15%), and a decrease in barren land (11.46%) and forest (1.42%). To simulate the changes in the runoff, the classified LULC image for the year 2000 is used in the SWAT model during the calibration (from 1995 to 1999) and validation (from 2000 to 2005). The performance results of the model are evaluated with statistical indicators R2 and NSE, and the value 0.73 and 0.83 during the calibration and 0.70 and 0.84 during the validation period was achieved. Further, the model is simulated using classified LULC image of the year 2015 to assess changes in annual runoff; it is observed a decrease in annual runoff in the study area with respect to changes in LULC.

Mid-Holocene palaeohydrochemistry and palaeohydrology of Yamdrok Yumtso, southern Tibetan Plateau, reconstructed from δ18O and δ13C of fossil shells of the gastropod Radix auricularia

Palaeohydrochemical and palaeohydrological changes of lakes have seldom been reconstructed from the fossil shells of the gasropod Radix auricularia, which is a new, and potentially high-resolution environnmental archive. We conducted a geochemical and stable isotope study of the shells of Radix from the exposed fluvio-lacustrine sediments near Lake Yamdrok Yumtso in the southern Tibetan Plateau. Our aims were to determine the sedimentary environment, palaeo-lake hydrochemistry and hydrological status. AMS 14C and OSL dating indicates that a lake-level stage of Yamdrok Yumtso higher than that of today occurred during ~4.7–1.2 cal. kyr BP. Results of Sr/Ca, δ13C and δ18O analysis of the fossil shells of Radix auricularia indicate that the lake-level fluctuations were mainly controlled by changes of the Indian Summer Monsoon; decreasing evaporation during the mid- to late-Holocene was also responsible. In addition, based on the geochemical relationship between Radix sp. shells and the ambient water in lakes, the values of δ18OPalaeo-water and Sr/CaPalaeo-water reconstructed using the fossil shells of Radix auricularia are −8.2‰ to −5.1‰ and 0.0012 to 0.0057, respectively. Further, based on the values of δ18Oshell, together with geomorphological evidence, we infer that Yamdrok Yumtso was a closed lake system, and we estimate its possible extent during the interval of high lake-level. In addition, we speculate that the water level of Yamdrok Yumtso at this time exceeded 4448.9 m a.s.l., but was less than 4451 m a.s.l., and that the major separation of various components of the Yamdrok Yumtso system occurred after 1.2 kyr BP.

The Stream Length Duration Curve: A Tool for Characterizing the Time Variability of the Flowing Stream Length.

In spite of the importance of stream network dynamics for hydrology, ecology, and biogeochemistry, there is limited availability of analytical tools suitable for characterizing the temporal variability of the active fraction of river networks. To fill this gap, we introduce the concept of Stream Length Duration Curve (SLDC), the inverse of the exceedance probability of the total length of active streams. SLDCs summarize efficiently the effect of hydrological variability on the length of the flowing streams under a variety of settings. A set of stochastic network models is developed to link the features of the local hydrological status of the network nodes with the shape of the SLDC. We show that the mean network length is dictated by the mean persistency of the nodes, whereas the shape of the SLDC is driven by the spatial distribution of the local persistencies and their network‐scale spatial correlation. Ten field surveys performed in 2018 were used to estimate the empirical SLDC of the Valfredda river (Italy), which was found to be steep and regular—indicating a pronounced sensitivity of the active stream length to the underlying hydrological conditions. Available observations also suggest that the activation of temporary reaches during network expansion is hierarchical, from the most to the least persistent stretches. Under these circumstances, the SLDC corresponds to the spatial Cumulative Distribution Function of the nodes persistencies. The study provides a sound theoretical basis for the analyses of network dynamics in temporary rivers.

Scientific cruise research 2019

The article provides information on the first results of the study of bottom material taken during geological works in the framework of complex research expeditions "Danube-2019" and "Black Sea-2019" in accordance with the Agreement on Scientific and Technical Cooperation between Scientific Hydrophysical Centre of the National Academy of Sciences of Ukraine and State Hydrography Service. The purpose of expeditionary geological research was to obtain relevant empirical data on general trends in changes in bottom topography and main features of floor surface and sedimentation.Comprehensive expeditions collected factual data on the hydrographic, hydroacoustic and hydrological status of the studied waters and in a test mode made geological sampling of the bottom of the North-Western shelf coastal part of the Black Sea and the Danube mouth (within Ukraine) using developed and prepared equipment. Information about the works was added to the oceanographic data bank of the National Academy of Sciences of Ukraine. The practical significance of the obtained results is to field test the technology of geological sampling and further cameral work.

Modelling of flood propagation in a semi-arid environment case of the N'FIS basin - Moroccan Western high atlas

The modelling of flood propagation in semi-arid environments can be extremely useful for a better assessment and flood risk planning to reduce the catastrophic impacts of this phenomenon. The main purpose of this work is to make a comparative study between two different models in order to choose the most suitable one for the monitoring of the hydrological status of N'fis watershed and for the optimal management of the dam reservoir of Wirgane during flooding periods. In this work, the modelling of the phenomenon of flood propagation is carried out by two models Hayami and Muskingum. Our analysis of the models first passes through a calibration process that is based on the identification by Genetic Algorithm (GA) the optimal parameters, the second phase is validation by testing the deliverability of the models through the parameters of the previous phase, the last phase consists of evaluating the models by performance criteria. The results obtained show that the parameters optimized by the GA, K (storage constant) = 11,580 and x (weighting factor) = 0.14 for Muskingum and C (Celerity) = 3 and D (Diffusion coefficient) = 3200 for Hayami, are found to have a better response with a Nash greater than 0.7 and a correlation coefficient d of Order 0.9. According to the sensitivity test, the parameters K and C remain parameterized with the greatest sensitivity. In general, the comparison of the two models shows that the Hayami model is easy to manipulate to simulate flood routing; this aptitude makes it one of an interesting tool capable of adequately representing the behaviour of floods in semi-arid environment

Lake Water Levels and Associated Hydrologic Characteristics in the Conterminous U.S.

Establishing baseline hydrologic characteristics for lakes in the U.S. is critical to evaluate changes to lake hydrology. We used the U.S. EPA National Lakes Assessment 2007 and 2012 surveys to assess hydrologic characteristics of a population of ~45,000 lakes in the conterminous U.S. based on probability samples of ~1,000 lakes/yr distributed across nine ecoregions. Lake hydrologic study variables include water-level drawdown (i.e., vertical decline and horizontal littoral exposure) and two water stable isotope-derived parameters: evaporation-to-inflow (E:I) and water residence time. We present 1) national and regional distributions of the study variables for both natural and man-made lakes and 2) differences in these characteristics between 2007 and 2012. In 2007, 59% of the population of U.S. lakes had Greater than normal or Excessive drawdown relative to water levels in ecoregional reference lakes with minimal human disturbances; while in 2012, only 20% of lakes were significantly drawn down beyond normal ranges. Water isotope-derived variables did not differ significantly between survey years in contrast to drawdown. Median E:I was 20% indicating that flow-through processes dominated lake water regimes. For 75% of U.S. lakes, water residence time was < 1 year and was longer in natural vs. man-made lakes. Our study provides baseline ranges to assess local and regional lake hydrologic status and inform management decisions in changing environmental conditions.

On the impact of increasing drought on the relationship between soil water content and evapotranspiration of a grassland

AbstractWeighable lysimeters were used to study the relation between soil water content (SWC) and the actual evapotranspiration (ETa) of grassland under two different climate regimes of Rollesbroich and Selhausen but for an identical soil from Rollesbroich. All components of the water balance were determined from 2012 until 2018. Budyko analysis was used to characterize the hydrological status of the studied sites. Wavelet analysis was also applied to study the power spectrum of ETa, vegetation‐height‐adjusted reference evapotranspiration (ETcrop), and water stress index (WSI) defined as ETa/ETcrop, as well as SWC at three different depths and the coherence between SWC and ETa and WSI. The Budyko analysis showed that 2018 resulted in a shift of both locations towards more water‐limited conditions, although Rollesbroich remained an energy‐limited system. Based on the power spectrum analysis, the annual timescale is the dominant scale for the temporal variability of ETa, ETcrop, and SWC. The results also showed that increasing dryness at the energy‐limited site led to more temporal variability of SWC at all depths at the annual timescale. Wavelet coherence analysis showed a reduction of the phase shift between SWC and ETa at an annual scale caused by the increase in dryness during the measurement period. We found that phase shifts between SWC and ETa and SWC and WSI were stronger at the water‐limited site than at the energy‐limited site. The wavelet coherence analysis also showed that from 2014 to 2018, the control of ETa and WSI on SWC increased due to higher dryness of soil.