Water Recession Research Articles

Threshold responses and relationships between waterbird distribution and habitat factors at Shengjin Lake, China

The wintering period is an essential part of the annual life history of waterbirds. The environmental conditions of habitats in winter directly affect the abundance and physical condition of waterbirds. Therefore, it is important to study the relationship between waterbird abundance and habitat factors. In this study, we conducted significance and threshold analyses between habitat factors and the waterbird community at Shengjin Lake, a Ramsar Site in China, using Redundancy Analysis (RDA), Spearman Correlation Analysis, and Threshold Indicator Taxa Analysis (TITAN). The results indicate that seven environmental variables significantly affected the abundance of waterbird communities, that is, fractional vegetation cover, degree of receding water, grassland area, mudflat area, shallow water area, deep water area, and distance to reeds. Waterbird communities exhibited significant threshold responses to all seven factors. The number of species significantly responding to different habitat factors varied among waterbird communities, with the highest number of species (15) responding to distance to reeds. Except for the deep water area and distance to reeds, waterbirds showed higher positive than negative thresholds for the remaining five factors. Different groups of waterbirds influenced the threshold responses of waterbird communities to habitat factors, and there were variations in how each waterbird group responded to these factors. The results of this study highlight the importance of habitat type, water recession degree, and shelter conditions in waterbird habitat selection. Minor differences in habitat structure can influence waterbird habitat preferences. Therefore, wetland management at Shengjin Lake should consider the specific habitat needs of different waterbird species.

Sosialisasi Penguatan Wawasan Kesiapsiagaan Bencana dalam Merespons Desa Tanggap Bencana di Desa Doyong Kabupaten Sragen

Desa Doyong is one of the villages located in Miri District, Sragen Regency, Central Java. The natural disaster of flooding in Doyong Village occurred in 2023, with a prolonged water recession process. Besides floods, droughts and strong winds also occurred due to extreme weather. The community's unpreparedness in facing disasters resulted in social and economic impacts. Therefore, the purpose of this community service is to enhance the knowledge, abilities, and independence of the community in facing and addressing disaster issues, as well as to build community preparedness for potential future disasters. The research employs a descriptive qualitative approach, collecting primary data through in-depth interviews, observations, and focus group discussions (FGDs). Secondary data were obtained from official BPBD documents, documentation, and relevant literature. Activities included rainfall mapping, community and school disaster preparedness education, the Village Clean Week (GUBERDES) program, reforestation, and collaboration with BPBD Sragen Regency. Results indicate that effective resource mobilization and involvement of various stakeholders, can improve community disaster preparedness.

Influence of the hydrological regime of lake buyo on fish community of three floodplains in the Tai national park (southwestern Côte d’Ivoire)

Floodplains play an important role in the ecological functioning of the areas on which they depend. These plains are also of socio-economic interest to the local population, particularly in terms of fishing activities. The fish fauna of three Lake Buyo floodplains (Néma, Libériakôbro and Gah) was studied in relation to the lake's hydrological regime. The aim of this study was to evaluate the influence of the hydrological seasons of Lake Buyo on the structure of the fauna considered. Sampling of fish community was carried out monthly during an annual cycle using experimental fishing. The structure of the fish community was analyzed by determining taxonomic composition, taxon abundances (Ar) and the Shannon-Weaver diversity (H') and Pielou equitability (E) index. Temporal dynamics of the studied parameters were analyzed according to three hydrological seasons: flood season, high water season and recession season. Results showed that total specific richness of ichthyofauna of the studied plains was 38 species, and the richness observed at the different hydrological seasons varied significantly (p < 0.05). The Cyprinidae family was dominant in the abundances recorded at all seasons (48.34% ≤ Ar ≤ 85.5%). It should be noted that the studied ichthyofauna exhibited relatively low diversity and equitability with reference to diversity index (1.42 ≤ H' ≤ 1.46 and 0.28≤ E ≤ 0.29).

Numerical simulation and characteristic analysis of flood intrusion into streets and buildings

In recent years, the study of urban floods has gained significant importance due to the impacts of climate change and rapid urbanization. A crucial task in accurately reproducing real-world urban flood events lies in enhancing the modeling capability to incorporate the entry of floodwaters into buildings through openings. This study presents a validated two-dimensional (2D) model based on the Shallow Water Equations (SWEs) to extend the numerical simulations beyond the analysis of water entering a single building to a cluster of buildings. The results confirm the feasibility of incorporating floodwater entering buildings processes in future urban flood simulations, thereby enhancing the realism of the outcomes. Moreover, this research delves into the characteristics of water depth and flow patterns not only on the streets but also inside the buildings. The investigation reveals that building openings play a vital role in the transportation and redistribution of floodwaters within the street network. Furthermore, variations in the rates of water level rise and recession inside buildings are observed, highlighting the influence of opening configurations and building locations. Additionally, a dynamic assessment of pedestrian risk throughout the flood duration is conducted, providing valuable insights and recommendations for disaster prevention and mitigation strategies during urban flood events. It serves as a valuable resource for urban planners and policymakers involved in the development of resilient cities in the face of increasing urban flood challenges.

Effect of Heterogeneity Due to Inappropriate Tillage on Water Advance and Recession in Furrow Irrigation

Effect of Heterogeneity Due to Inappropriate Tillage on Water Advance and Recession in Furrow Irrigation

Assessment of water level fluctuation impacts along River Nile, Egypt

ABSTRACT This paper aims to develop a computational model to assess and evaluate the annual water level fluctuation (WLF) impacts and their trends along any open channel (river, canal or lake) and provide reliable information that may help handle their implications. The impacts are related to water recession, flood plain areas, uncovered river bars and islands, locations of navigation bottle necks, and dredging works. The model is developed using Excel Spreadsheet VBA Coding. It computes the horizontal and inclined recession distances that govern water in take construction. It also computes the uncovered flood plain areas along the river reach to avoid encroachments and human interventions. In addition, it identifies the number of bar sand islands that emerge at low water levels to protect them against infringements. It also determines the locations of navigation bottle necks and computes the dredge volumes required. It can handle long river reaches quickly. Moreover, it is open-accessed where no hard locks or license renewals are required. It is run on Microsoft Excel which is an available and familiar environment to engineers. Therefore, the model can be a quick and powerful tool to support the decision-making process for projects related to such impacts, especially at the prefeasibility study stages. Reach '1' of River Nile in Egypt was taken as a case study to apply the model and show its capabilities in assessing the WLF impacts. This could help compute and analyze the size of the impacts and conceive their trends. Finally, the model could provide information about the impacts in concrete figures which can support decision making in coping properly with the impacts.

Drought-induced changes in hydrological and phenological interactions modulate waterbird habitats dynamics

Floodplain wetlands are essential for the survival and reproduction of waterbirds, but droughts can negatively impact their food availability and habitat conditions, leading to a decline in waterbird abundance and diversity. To better understand the impact of hydrological and phenological variables on floodplain waterbird habitats during drought conditions, we employed hydrological modeling and remote sensing techniques to calculate fine-scale environmental variables. We constructed habitat suitability models using nine years of field surveys of waterbirds and identified the impact of the interaction effects between hydrological and phenological variables on waterbirds under drought and non-drought conditions. The results showed that hydrological and phenological variables can provide useful information for quantifying the habitat suitability of waterbirds. Drought-induced early water recession negatively impacted the quality of waterbird habitats, reducing their habitat suitability. Sedge eaters exhibited the most significant reduction of 34.47% in the total area of the lake, followed by seed eaters, fish eaters and invertebrate eaters. Tuber eaters had the largest increasing trend, with a significant increase area of 7.44% in total area. Our findings suggest that various feeding guilds exhibit distinct interactions in response to drought, which can be strengthened or weakened by alterations resulting from drought. For sedge eaters, seed eaters, and fish eaters, drought could result in a faster decline in habitat suitability by strengthening the interaction effects between variables. In contrast, for invertebrate eaters and tuber eaters, drought could weaken interaction effects between variables, resulting in a slower decline in habitat quality. The results provide valuable insights into the spatial distribution of overwintering waterbirds and can inform conservation efforts in wetlands.

What Drives the Morphological Traits of Stress-Tolerant Plant Cynodon dactylon in a Riparian Zone of the Three Gorges Reservoir, China

The cyclical process of water storage and recession in the regular operation of the Three Gorges Reservoir creates a unique habitat stress that alters the structural and functional attributes of vegetation ecology within the riparian zone. The stress-tolerant plant Cynodon dactylon (L.) Pers is the dominant plant species in the riparian zone of the Three Gorges Reservoir. In this study, the riparian zone of the Daning River, a tributary located in the center of the Three Gorges Reservoir, was selected as our study area. To identify the drivers of the morphological traits of C. dactylon in the riparian zone of Daning River, we examined plant biomass and plant characteristics across different elevation gradients, with reference to abiotic factors to determine the distribution patterns of plant morphological traits. Results indicated that in the two main soil types of the riparian zone, plant biomass showed a consistent trend along the elevation gradient, with a “middle-height expansion” pattern; biomass increased and then decreased with rising water levels. Plant biomass positively correlated with soil total nitrogen and negatively correlated with soil pH, electrical conductivity, and total phosphorus. C. dactylon adapted to prolonged flooding in the riparian zone by having a significant negative correlation between plant height and erect stem length with soil moisture content to facilitate root respiration.

Soil‐water response in a volcanic ash hillslope affected by fissures and microtopographic changes caused by the Kumamoto earthquake, in Japan

AbstractWe examined soil‐water response in a hillslope with multi‐layered volcanic soils affected by fissures formed by intense shaking during the 2016 Kumamoto earthquake in Japan. Pressure head and volumetric water content responses in a 6 × 20 m hillslope ridgeline plot were monitored by tensiometers and capacitance‐based soil moisture sensors, respectively. The plot contained seven seismic fissures (0.3–0.8 m deep and 0.4–2.2 m wide) formed parallel to the ridgeline that exposed underlying soil layers, while areas with topsoil occurred between the fissures. Among the alternating layers, the andisol (ca. 1.0 m deep) consistently experienced high pressure heads (>−150 cm H2O) and volumetric water contents (>0.58 cm3 cm−3), indicating high water‐holding capacity. This andisol was a key layer for storing soil water and causing slow drainage into the deeper matrix, resulting in abrupt increases in volumetric water content during storms. Rainwater directly reaching the bottom of fissures without percolating through the topsoil caused rapid soil‐water response compared to the soil layer where water percolated via topsoil. Analysis of in‐situ soil water retention curves, recession rates and water storage changes revealed that the second andisol had unique characteristics for retaining water in the hillslope. The findings of this study show that spatial and temporal variability of soil water responses varied associated with earthquake‐induced fissure formation and soil water characteristics of multi‐layered volcanic soils.

Integrating suitable habitat dynamics under typical hydrological regimes as guides for the conservation and restoration of different waterbird groups

The operation of the Three Gorges Project (TGP) has influenced the wetland ecosystems downstream, thereby affecting the distribution of habitats suitable for waterbirds. However, dynamic studies on habitat distribution under different water regimes are lacking. Here, using data from three successive wintering periods representing three typical water regimes, we modelled and mapped the habitat suitability of three waterbird groups in Dongting Lake, which is the first river-connected lake downstream of the TGP, and a crucial wintering ground for waterbirds along the East Asian-Australasian Flyway. The results showed that the spatial pattern of habitat suitability varied among the wintering periods and waterbird groups. The analysis estimated the largest suitable habitat area for the herbivorous/tuber-eating group (HTG) and the insectivorous waterbird group (ING) under a normal water recession pattern, whereas early water recession had a more adverse effect. The suitable habitat area for the piscivorous/omnivorous group (POG) was higher under late water recession than under normal conditions. The ING was the most affected by hydrological changes among the three waterbird groups. Further, we identified the key conservation and potential restoration habitats. The HTG exhibited the largest key conservation habitat area compared to the other two groups, while the ING showed a potential restoration habitat area larger than its key conservation habitat area, indicating its sensitivity to environmental changes. The optimal inundation durations from September 1 to January 20 for HTG, ING and POG were 52 ± 7 d, 68 ± 18 d, and 132 ± 22 d, respectively. Therefore, the water recession starting in mid-October may be favourable for waterbirds in Dongting Lake. Altogether, our results can be used as guidance for prioritising certain management actions for waterbird conservation. Moreover, our study highlighted the importance of considering habitat spatiotemporal variation in highly dynamic wetlands when implementing management practices.

Variations of plant communities in diversity and composition along the western coast of Lake Khanka caused by high water level

Lake Khanka is the largest freshwater body of water in northeast Asia, with a basin of about 25 000 km2. The hydrological regime of the lake is cyclical in nature due to various factors affecting water inflow and outflow. The last increase of water level in the lake began in the 2000s and by 2015 reached the maximum value of 416 cm (with the average annual level of 293 cm). A steady decline in water level has been observed since 2021. To assess the diversity and structure of coastal plant communities on the sandy-pebbly substrate along the western shore of Lake Khanka and their dynamics under the influence of flooding, we laid 20 transects and performed descriptions at seven sites, including two sites in the protected area of the Cluster Sosnovy of the Khanka Nature Reserve. Using the diversity and similarity/difference indices, plant communities were compared across the sites. It was shown that their heterogeneity is due to the diversity of both aboriginal and adventive species. In protected areas, the role of adventive species is significantly lower than in recreational areas. The five dominant species in the communities account for 50 % or more of the total abundance. Vegetation groupings in the three identified zones, which have been inundated for different periods of time, have a similar diversity, with differences due only to the native fraction of species. The second zone, characterized by the greatest influx of species of different ecological and cenotic groups during water recession, differs in species richness. The obtained data show for the first time the diversity and structure of coastal plant communities of the sandy-pebble beech of the western coast of Lake Khanka and reflect some processes of its dynamics in connection with the long-term standing water. For more successful coverage of the issues raised, long-term monitoring on the laid transects, at least covering one 20–30-year cycle of the dynamics of the hydrological regime of Lake Khanka, is necessary.

Nest‐site selection model for endangered Everglade snail kites to inform ecosystem restoration

AbstractThe once vast and interconnected Everglades wetland ecosystem in Florida underwent a 50% reduction in area in the 1900s, resulting in a highly compartmentalized and managed system where ecological restoration is ongoing. Everglade snail kites (Rostrhamus sociabilis plumbeus, hereafter snail kites) are federally endangered wetland specialists with a single population in Florida, USA. Predictive models can help inform restoration and natural resource management decision‐making regarding both the quantity and timing of water delivered through the hundreds of water management structures in the Everglades. We developed a spatially explicit real‐time nest‐site selection model, KiteNest, using environmental predictors of nesting for snail kites in south Florida. The results of our modeling indicate that hydrology, percent canopy cover, and proximity to recently burned areas were the most important factors associated with nest‐site selection for snail kites. Water depths between 75 and 100 cm, water recession rates between 0 and 1.25 cm/day, percent canopy covers <20%, and areas <10 km from recently burned habitat were associated with the greatest likelihood of nest‐site selection. KiteNest is applicable to natural resource management decisions in the Everglades and may be useful independently or in conjunction with other ecological models for restoration decision support.

Study on the retention effect of condensed water at different soil levels in exposed areas of Hoh Xil lake upon water recession

Abstract In order to investigate the absorption and retention characteristics of condensed water at different soil layers in the bare desertification area at the bottom of a receding lake in Hoh Xil, Qinghai Province, the characteristics of condensate variation, condensate formation time, condensate volume, and its absorption capacity were investigated in July 2021 using a micro-osmometer. The research area was the artificial water retention layer and bare ground of the exposed sandy bottom formed under the influence of the warming–wetting trend that occurs when water recedes in the salt lake area of the Qinghai-Tibet Plateau, as well as the two conditions of underpass and underseal. According to the results, the time of condensation generation during the observation period in the salt lake area of Hoh Xil begins at about 0:00 and ends at about 10:00. The artificial water retention layer had little influence on the condensation generation time, and the trend of the condensation rate is the same. The unidirectional condensation phenomenon of water vapor in the near-surface air at a depth range of 0–5 cm when an artificial water retention layer is applied is clearly superior to that of other layers; accordingly, its frequency of condensation phenomenon is also the highest. The amount of condensed soil water vapor from the lower part of the ground when an artificial water retention layer is applied at depth ranges of 0–5 cm, 5–10 cm, and 0–10 cm were 3.60, 6.39, and 10.27 times that of the near-surface air, respectively. The total amount of bidirectional condensed water under the condition of the artificial water retention layer at 0–10 cm was the largest. Conversely, the total amount of condensed water from the near-surface air at a depth range of 0–5 cm under the unidirectional condensation condition was the highest, being twice as great as the total amount of condensed water in other layers, which demonstrates the promoting effect that the artificial water retention layer has on the adsorption of water vapor in the near-surface air. Due to the existence of permafrost in the Qinghai-Tibet Plateau, the heat zero-flux plane in the area of the Salt Lake has a migration range of divergence of approximately 30 cm from the surface to the ground. An analogous humidity coefficient characterizes the retention effect of condensed water in certain areas, which serve to demonstrate how the artificial water retention layer distributed at a depth of 0–5 cm, regardless of bidirectional or unidirectional condensation, has the best capacity for adsorption. The results of this study provide a theoretical basis for condensate absorption capacity and vegetation restoration in the bare ecologically degraded areas of the lake bottom.

Impact of water recession and drying on some physical and chemical properties of Abu – Zarak marsh

This study was conducted to investigate the effect of drying and water ebb on some chemical and physical properties of Abu – Zarak marsh. The results showed that the studied pedons characterized by loam texture domination which take gradual trend , wherever texture coarseness increase with increment of distance from marsh center , higher clay percentage found in pedon No.3 which locate in the center of marsh and that is expected because of sedimentation nature and particle translocation gradually with water ebb front . Soil reaction (pH) ranged between (7.46 – 8.00) that’s indicate the studied soils was alkaline because of high percentage of calcite , the results showed that the soil pedons characterized by high values of electrical conductivity (Ec) which ranged between (31.7-70) , (27.3-52.2) , (25.9-94.7) for pedons 1,2,3 respectively. Calcium carbonate ranged between (17-40%) and higher percent recorded in the surface horizon for pedon 2 and lower percent recorded in its followed horizon. This highness produced by parent material effect as add to drying factor which increase calcification process activity. In the other hand the organic matter content was varied between studied pedon 2 (1.7%) and these percents was low as compared with expected values in marsh soils. The results indicate that the cations concentrations varied according to the distance from marsh center and higher percent found in pedon 1 which was (150 , 570 , 180 , 1478 meq/L) for Ca , Mg , K , Na ions respectively , and higher percent of anions which was (1705 , 220 , 0 , 2.8 meq/L) for Cl , So4 , Co3 , Hco3 respectively. The other results showed that the nitrate ion differ from other ions by higher values recorded in the far pedon from marsh center where is pedon 3 which was 307.5 ppm while in the pedon 1 at the center of marsh was 2.5ppm.

Application of Potassium after Waterlogging Improves Quality and Productivity of Soybean Seeds.

Potassium (K) improves the stress tolerance of crop plants, which varies on the timing of K application and crop varieties. Soybean is a promising crop that can easily fit with the cropping pattern during kharif I season, when water logging occurs due to sudden rain. Therefore, an experiment was conducted to determine the effect of K management on the productivity and seed quality of soybean under normal and waterlogged conditions. The treatments comprised three factors, namely soybean genotypes (BU Soybean-1 and BU Soybean-2), waterlogging (WL) (control and WL for 4 days at the flowering stage (FS)), and K application (full dose as basal and 50% as basal +50% as top dress after termination of the flooding). The trial was laid out in a randomized complete block design with three replications. Findings revealed that BU Soybean-1 produced a higher number of pods and seeds pod-1 under control conditions with basal application of K. On the other hand, BU Soybean-2 produced taller plants and heavier grain, improving grain and straw yield under WL conditions when K was top dressed. The varieties absorbed a higher amount of nitrogen, phosphorus, and potassium under control conditions compared to WL when K was top dressed. Similarly, the seed protein content of both varieties was higher in the control condition with a top dressing of K. However, a higher percentage of seed germination was obtained from BU Soybean-2 in the control condition with a top dressing of K. Further, more electrical conductivity and more mean germination time were recorded in the case of BU Soybean-2 under WL with the basal application of K. Split application of 50% of recommended K fertilizer after the recession of flood water could be suggested for improved grain yield in flood-affected soybean growing areas.

Determination of Irrigation Lengths in Vertisol Soils Using the Two-Point Infiltration Method and Kostiakov-Lewis Equation

Vertisol soils, which cover large lands in irrigated areas in Turkey and the world, swell when wet and form deep cracks when dry. These properties of Vertisol soils cause a significant decrease in irrigation efficiency when irrigating with surface irrigation methods, thus causing water insufficiency and drainage problems. If appropriate irrigation time, flow rate and furrow-border lengths are used, water application efficiency can be increased in these soils. For this purpose, two-point infiltration tests were carried out using 120 m long, 0.5-0.6% slopping furrows. A constant water level orifice was used to keep the flow rate unchanged during the tests. Water advanced and recession times were observed and recorded at stations created at 20 m intervals. Before and after the test, the cross-sectional area of the furrow was measured with a rill-meter. By evaluating the obtained data, the Kostiakov-Lewis infiltration equation, which is expressed as Z = 0.00822 τ 0.27695 + 0.00048 τ equation, was obtained. With the determined equation, the optimal irrigation length was estimated to be approximately 85 m for 90% water application efficiency and 115 m for 80% water application efficiency, using the advance and recession curves.

Improvements in the degree-day model, incorporating forest influence, and taking China’s Tianshan Mountains as an example

Study regionKunes River Basin in the western Tianshan Mountains, China. Study focusThe study used atmospheric meteorological data such as temperature, radiation and snow melt rate for areas with different degrees of openness. The climatic parameters, snow melt process, and major environmental controls were studied. By analysing an improved degree-day model that simulated the forest subcanopy, a subcanopy snowmelt model was constructed. New hydrological insights for the regionThe net shortwave radiation of snowy subcanopy surfaces is lower than that of open sites, whilst the net longwave radiation is higher. This suggests that the influence of longwave radiation on the snowmelt process in the subcanopy is greater than that of shortwave radiation. Furthermore, due to the relatively high night-time temperatures in the subcanopy, the influence of the water recession process was significant. In this study, net longwave radiation and water recession were added to a traditional degree-day model. The simulation showed that the improved degree-day model responded well. The R2 of each station was > 0.88, the Ens was > 0.87, and the PBIAS was 0.63 %− 8.44 %, providing a simple and feasible method for the simulation of snowmelt runoff.

Responses of urban flood processes to local land use using a high-resolution numeric model

Rapid increase of urban impervious surface, resulting from unplanned urban sprawl, leads to the frequent occurrence of urban flood disasters caused by abnormal precipitation in flood season. In this work, a coupled urban rain flood model and normal pipe network model is employed to simulate the city inundation and pipe network hydrodynamics under different local land use types. The results shows that the peak surface inundation and pipe network outlet flow after transformation were 4.36%–42.43% and 0.01%–1.34% higher than those before transformation for P ≤ 20, and its corresponding values reached 1.24%–5.59% and 27.26%–35.21% for P > 20. The change in land use types in local areas significantly impacted inundation of the whole surface under normal rainfall (P < 20), which was also verified by the water recession coefficient. In addition, land use transformation slightly affected urban inundation for P ≥ 100, which indicates that low-impact development facilities were almost ineffective in addressing inundation under extreme rainfall. A significant impact on the pipe network discharge was observed under the high rainfall return period (P ≥ 20). The recession coefficient obtained via coupled model simulations can be effectively applied in the urban flood recession process.

Changes in nonlinearity and stability of streamflow recession characteristics under climate warming in a large glaciated basin of the Tibetan Plateau

Abstract. The accelerated climate warming in the Tibetan Plateau after 1997 has profound consequences in hydrology, geography, and social wellbeing. In hydrology, the change in streamflow as a result of changes in dynamic water storage that originated from glacier melt and permafrost thawing in the warming climate directly affects the available water resources for societies of the most populated nations in the world. In this study, annual streamflow recession characteristics are analyzed using daily climate and hydrological data during 1980–2015 in the Yarlung Zangbo River basin (YRB) of the southern Tibetan Plateau. The recession characteristics are examined in terms of dQ/dt = − aQb and the response/sensitivity of streamflow to changes in groundwater storage. Major results show that climate warming has significantly increased the nonlinearity of the response (b) and streamflow stability [log(a)] in most subbasins of the YRB. These changes in the recession characteristics are attributed to the opposite effects of increases in the available water storage and recession timescale on the recession. Climate warming has increased subbasin water storage considerably due to more recharge from accelerated glacier melting and permafrost thawing after 1997. Meanwhile, the enlarged storage lengthens recession timescales and thereby decreases the sensitivity of discharge to storage. In the recession period when recharge diminished, increased evaporation and the decreased buffering effect of frost soils under warmer temperatures accelerate the initial recession of streamflow. By contrast, enlarged storage and lengthened recession timescales slow down the recession. While reservoir regulations in some basins have helped reduce and even reverse some of these climate warming effects, this short-term remedy can only function before the solid water storage is exhausted should the climate warming continue.

Processes of preferential flow in a eurasian steppe under different scenarios

The control mechanisms of temporal and small-scale spatial characteristics on different types of preferential flow (PF) processes during infiltration are still lacking. Two-year high-resolution in situ soil moisture profiles were used to investigate the controls of PF processes and its interaction with moisture and vegetation dynamics, which covers three hillslope positions (upslope–14˚, midslope–9˚, and downslope–4˚) and three vegetation treatments (bare ground, stubble grassland and natural grassland) in a typical semi-arid grassland of Eurasia. Two types of PF were identified. Non-sequential response (NSR) was taken as one indication of PF using the disordered response of soil moisture profiles to rainfall. Fast preferential flow in sequence response (PF-rate) was taken as another indicator when a measured maximum pore water rate higher than saturated hydraulic conductivity. The conditions for the occurrence of the two PFs were inconsistent and different from the studies which showed the higher probability of PFs under dryer conditions and with higher rainfall intensities. Small rainfall events with low rainfall intensity and relatively low soil moisture at most locations showed higher NSR frequency, which further highlight the strong dependence of NSR on hydrophobicity and macropore structure of the topsoil. Whereas a higher rainfall intensity increased PF-rate under wet conditions. Meanwhile, the occurrence of PF-rate was also significantly controlled by vegetation coverage, soil texture and saturated hydraulic conductivity of 5–10 cm soil layer. Furthermore, the frequency of PF was 15.9%–44.5%, and its contribution to the total infiltration was >50%. The water recession rate of NSR and PF was slower and faster than that of matrix flow, respectively. This demonstrates the importance of PF to water replenishment in scarce rain areas and the influence of combinations of spatial–temporal factors on different flow processes.