Ecohydrology最新文献

Although physical barriers are being commonly used for fish protection and guidance of larger migratory species in hydropower plants, there is a lack of information on how they perform for small-bodied fish species. Here, we tested a small-bodied species (Alburnus escherichii) based on 30 individuals across 16 hydraulic treatments. These included screen angles of 22°, 30°, 38° and 45°, as well as bed slopes of 0% and 1% without a weir. Additionally, the efficacy of crump vs. streamlined bypass weirs was examined at a bed slope of 1%. All trials were video-recorded for analysis of bypass efficiency. For all tested conditions, we found a fish protection efficiency of 100%. Results showed that 38° and 45° screen angles produced the most favourable velocity distribution—reducing approach velocities from ~0.5 m/s (30°) to ~0.4 m/s—and increased passage efficiency. Raising the bed slope from 0% to 1% elevated approach velocities and reduced efficiencies by 10%–23% across all angles. The incorporation of a weir generated a beneficial backwater effect, yielding a 9%–15% improvement over the no-weir condition, with the streamlined profile outperforming the crump weir. Moreover, 38° screen angle has the shortest fish passage time for all tested configurations. These findings provide clear design guidelines—namely, a 38° fine-screen rack, minimal inlet slope and a streamlined bypass weir—to optimize downstream fish guidance and mitigate injury and mortality in run-of-river hydropower installations.

Root water uptake (RWU) is a critical ecohydrological process, yet its quantification under field conditions remains challenging. Profile soil moisture dynamics offers a viable approach to estimating RWU via analysing diurnal moisture fluctuations. While validated in humid forests, the applicability of this method in other environments, such as shrubs in semi-arid areas, remains underexplored. Focusing on the Chinese Loess Plateau (CLP), a key region for ecological restoration, we evaluated the utility of soil moisture to quantify RWU for Vitex negundo, a dominant xerophytic shrub. Soil moisture was monitored at two profiles (50 and 130 cm from the shrub) across five root-zone depths during the 2022 growing season. By carefully revising the established method, we developed three methods to quantify daily shrub RWU dynamics and validated them against sap flow measurements. Results revealed that the method incorporating fixed RWU start/end times and daytime soil moisture trends outperformed others and was recommended for follow-up studies. Our findings validate the efficacy of profile soil moisture data for quantifying shrub RWU in semi-arid environments and identify key influencing factors, that is, soil moisture status and sensor placement. RWU estimates from the 50-cm profile exhibited a stronger correlation with sap flow (r = 0.63) compared to the 130-cm profile (r = 0.22). This correlation further intensified under high soil moisture conditions without precipitation (r = 0.80 vs. 0.34). This study advances methodological frameworks for RWU estimation in water-limited ecosystems, offering insights to enhance ecological restoration on the CLP.

Amid worsening drought conditions driven by climate change, water-retaining soil amendments are increasingly needed. This study aimed to examine the characteristics of plant-available water in soil amended with a superabsorbent polymer (SAP) under two distinct treatments: (1) seedling growth with intermittent watering after planting (watering period) and (2) time to wilting and death following the cessation of watering (drought period). Japanese cedar (Cryptomeria japonica), a water-demanding species, and drought-tolerant Japanese cypress (Chamaecyparis obtusa) were planted in pots containing sandy soil mixed with four levels of SAP. During the watering period, higher SAP addition rates led to increased soil moisture content and water potential. Seedlings exhibited elevated evapotranspiration rates and enhanced growth, particularly in fine root development. In the drought treatment, soil moisture and water potential declined rapidly. The median time to death was extended by up to 12 days for cedar and 3 days for cypress compared to the control. SAP effects were more pronounced in cedar than in cypress. Most of the water retained in SAP-amended soils was categorised as high-potential, immediately available water (> −38 kPa). Conversely, the amount of readily available water (−38 to −98 kPa) decreased, whereas hardly available water (< −98 kPa) remained unchanged. In conclusion, SAP amendments promoted fine root development and improved survival in water-demanding cedar but had limited effects on the drought-tolerant cypress. To better address drought risks in seedling planting, the development of SAPs with enhanced water retention, especially at lower water potentials, is necessary to meet practical expectations.

Liverworts belong to the oldest vascular-free bryophytes, and thus with their preserved and unique hydrological processes, they may be the most appropriate models of plant–ecosystem interaction. Their adaptability and their simple morphology are conducive to a detailed structural examination. Some species of liverworts (Calypogeia arguta, Metzgeria conjugata, Clevea hyalina and Riccia papillosa) are mentioned for the first time in Uzbekistan. Annotation contains the data about their distribution, habitat, and location. The paper introduces the novel records of four liverworts, and their analysis by stereomicroscopy and light microscopy (LM). The new species recorded were C. arguta, M. conjugata, C. hyalina and R. papillosa. Microscopy characterization visualized detailed data on the following leaf characteristics: C. arguta presented minute papillae and irregular cells of the epidermis; M. conjugata presented a surface of high texture with small protrusions; C. hyalina presented a smooth shiny surface with only surface structures; and R. papillosa presented a rough texture surface with closely packed papillae. The results broaden the hypothesis of the bryoflora according to which the liverworts, due to the target micromorphological changes, can serve minor functions in the control of moisture in the microhabitat and during the initial phases of ecological vegetation and stability in riparian habitat.

Plant surface water storage (PWS) greatly affects canopy rainfall interception and thus has a significant impact on water availability for plants under drought conditions. However, it remains unclear whether the responses of PWS characteristics of dioecious plants exhibit sexual dimorphism under drought stress and how these responses relate to plants' drought resistance. To this end, the impact of drought on the PWS characteristics, related leaf traits and biomass accumulation of Spinacia oleracea males and females was investigated. Under normal water conditions, PWS per unit total dry weight and per unit leaf area of females were 52.8% and 42.1% lower than those of males, respectively, indicating a potentially higher PWS efficiency of males. Under drought conditions, PWS per unit total dry weight and per unit leaf area in males decreased significantly by 24.9% and 62.7%, respectively, while those in females remained unchanged, implying greater sensitivity of males' PWS efficiency to drought. The PWS capacities of the stem, leaves and entire plant were similar between males and females under normal water conditions, but the males exhibited a greater reduction under drought. Female plants showed a 20.4% lower reduction in leaf dry weight and a stronger increase in leaf density under drought than males, reflecting stronger drought resistance in females. Analysis based on leaf hydraulic characteristics suggested that both sexes might enhance their foliar water uptake, as indicated by larger contact area of water drop on leaf surface due to improved leaf wettability (lower leaf contact angles) and better structural basis for foliar water absorption due to higher leaf succulence indexes under drought. However, females might benefit more from these adaptations due to their undiminished PWS efficiency. These results suggested that deriving greater benefits from foliar water uptake through maintaining stable rather than decreased PWS efficiency may be one of the reasons why female S. oleracea plants exhibit stronger drought resistance than the males.

These days, Indian rivers are under tremendous stresses as increasingly larger quantities of water are withdrawn to meet ever-increasing demands caused by population and industrial growth, flow regulation and fragmentation, land-use changes, sediment mining and changing climate. One way to keep rivers healthy is through environmental flows (Eflows), whereby time- and space-varying quantities of water are released into the river to maintain its ecosystem. This paper discusses the Eflows concept and estimation methods. Selected case studies from India have been described in which the methods used include hydrological, hydrology + hydraulics and Building Block Method. A detailed analysis of Eflows assessment for the Ganga and Yamuna rivers has been presented keeping in view the practical aspects. I suggest that Eflows assessments should consider physical processes such as river–aquifer interaction, particularly in the case of alluvial rivers. Water quality aspects may also be considered if water quality degradation is due to changes in flow regimes. Keeping in view the large size of India, variability and the number of rivers, there is a need to determine Eflows requirements for different river reaches in the country. The paper has also discussed barriers to Eflows assessment and implementation, technical and policy-related challenges and follow-up actions for wider Eflows implementation. For successful Eflows implementation, the general public needs to be associated with environmental preservation.

Freshwater ponds are prevalent globally and provide critical ecosystem functions (e.g., water storage and groundwater recharge), yet little is known of their hydrological features immediately following formation. We analysed stable isotopes of water (δ²H, δ¹⁸O) to characterize spatio-temporal hydrologic variation in ponds created by the Mount St. Helens eruption. We also examined how climate and landscape features interact to regulate local hydrology. Ponds were sampled for isotopic analysis in spring (2015, 2017, 2018) and summer (2018). Mass balance models characterized the water balance of ponds (evaporation:inflow; E:I), as well as water sources (rain, snow). Other variables were measured in situ (temperature, conductance), collected from data sources (meteorology) or quantified with remote sensing (vegetation). Bayesian estimates of standard ellipse areas (SEA_B) were used to compare isotopic values among years, whereas linear models were used to examine local and regional drivers of E:I, as well as intra-annual isotopic shifts. We observed high interannual variability (as SEA_B), suggesting that snow was the main water source in wet years but that the proportion of rain and snow varied among sites in dry years. Spring E:I was negatively correlated with total precipitation, whereas the importance of evaporation in summer varied with pond morphology, with large shallow ponds exhibiting the greatest evaporation. Evaporation regulated the hydrology of ponds with higher dissolved organic carbon (DOC; as residuals of DOC and chlorophyll). We show that simple metrics of basin morphometry can predict seasonal variability in pond hydrology, allowing managers to better estimate pond sensitivity to future climate conditions.