Hydrological Processes最新文献

Urban tree transpiration (T) can significantly lower urban temperatures and mitigate the urban heat island effect. The careful selection of suitable tree species for the urban landscape holds immense significance in enhancing the quality of the human living environment. However, there remains a deficit of effective models capable of accurately assessing urban T and its associated cooling effects. In this study, we have developed a modified Priestley–Taylor (P–T_mc) model to assess T. This P–T_mc model calculates the vegetation P–T coefficient (α_v) through a machine learning technique that incorporates soil, meteorological, and vegetation parameters. Moreover, the P–T_mc model integrates CO₂ concentration and flux data to enhance the precision of T simulations. Upon validation using data from two eddy correlation (EC) sites and stable hydrogen and oxygen isotope observation sites, it was demonstrated that the P–T_mc model exhibits enhanced simulation capabilities for T when contrasted with the original P–T model. The root-mean-square error (RMSE) for the P–T_mc model was determined to be 0.025 mm/hf in T simulation. The transpiration and cooling effectiveness of 19 representative urban tree species were further assessed using the P–T_mc model framework. Among the selected 19 urban tree species, Ficus virens demonstrated the most impressive cooling performance. For Ficus virens, the average vegetation latent heat flux (λT) was measured at 6.18 MJ m²/d, while the temperature reduction (ΔT) reached 4.66°C m²/d. In contrast, Palmae exhibited the least effective cooling, with average λT and ΔT values of only 0.89 MJ m²/d and 0.67°C m²/d, respectively. Correlation analysis indicated that the cooling effects of various urban tree species were primarily influenced by tree morphology. Specifically, higher values of leaf area index (LAI) and crown area (C_a) were associated with better cooling performance, while increased tree height led to reduced cooling effectiveness. This study conducted a comprehensive evaluation of the cooling effects exhibited by diverse urban tree species through the utilisation of the proposed P–T_mc model. The outcomes of our investigation offer a more robust scientific foundation for urban landscape planning and the selection of tree species.

Groundwater supplies over 90% of Costa Rica's drinking water and supports vital ecosystem services, yet many aquifers, especially in high-altitude headwater catchments, remain understudied. This study aimed to (i) characterize the hydrogeochemistry and isotopic composition of the Poás volcanic aquifer system (PVAS), (ii) identify the key drivers controlling the chemical and isotopic evolution within the groundwater flow, and (iii) understand recharge governing processes, including mean potential recharge elevations (MREs). Groundwater across the PVAS consistently showed a predominant bicarbonate-calcic-magnesic facies, with chemical evolution primarily driven by carbonate and silicate weathering. Moderately high levels of nitrate and Escherichia coli in more than 56% of the samples indicate anthropogenic pollution legacy. Stable isotope compositions revealed altitude-dependent recharge patterns influenced by Pacific and Caribbean moisture sources. Isotope-inferred MREs ranged from 768 to 2407 m a.s.l. with a mean of 1549 ± 227 m a.s.l., overlapping a diverse land use mosaic. These findings demonstrate the high vulnerability of the PVAS to anthropogenic contamination and its reliance on high-elevation recharge. The integration of hydrochemical, isotopic, and multivariate statistical analyses establishes a transferable framework for the Central America Volcanic Arc region to identify groundwater chemical evolution, assess anthropogenic impacts, and better understand recharge dynamics. This framework supports local and regional water management agencies in prioritizing conservation efforts within recharge zones and in strengthening contingency plans for drought and contamination events across urban and peri-urban settings.

As an indispensable resource underpinning the sustainable development of Golmud City and its surrounding regions, the Golmud River water plays a pivotal role in maintaining regional ecology, facilitating economic development and ensuring social welfare. To provide scientific guidance for local water resources management, the intra-annual variations of the Golmud River water isotopes were investigated during 2019 to identify recharge sources and quantify evaporation impacts. Temporally, river water exhibited higher δ²H and δ¹⁸O values in July compared with other months. Spatially, δ²H and δ¹⁸O values of river water were the lowest in Xiaonanchuan (δ²H: −71.59‰ to −56.62‰, δ¹⁸O: −11.84‰ to −9.46‰), the highest in Yeniugou (δ²H: −66.2‰ to −46.79‰, δ¹⁸O: −10.98‰ to −6.52‰) and were between them below Nachitai. River water isotopes plotted below the local meteoric water line, and lc-excess decreased from upper to lower reaches, indicating intensified evaporation along the flow path. Isotope-altitude analysis showed the mean recharge elevation of river water exceeded 4700 m. MixSIAR modelling demonstrated that glacial meltwater (contribution: 29%–57.5%) and groundwater (contribution: 28.6%–46.8%) constituted primary recharge sources to river water for all the months, with enhanced precipitation contribution (24.2%) in July. Evaporation assessment revealed that the watershed-scale evaporation loss averaged approximately 9%, remaining negligible in Xiaonanchuan while attenuating along the water flow in Yeniugou, with the highest value reaching 22% near Kunlun Lake and 25.8% in the downstream (east branch). The evaporation loss stability of the middle reach suggested the possibility of glacial meltwater recharge to river water through faults. The combined use of the Rayleigh fractionation model and lc-excess was highlighted as a potential approach for river evaporation assessment. The findings advance the understanding of water cycling in arid-alpine watersheds and provide critical insights for optimising regional water allocation.

Soil erosion is a major environmental concern in tropical mountain ecosystems where steep terrain, intense rainfall and dynamic land use changes contribute to the accelerated degradation of natural resources. This study assesses the spatiotemporal patterns of potential soil erosion in the Tapesco River watershed, a peri-urban territory located in Costa Rica's Central Volcanic Mountain Range, for the years 1986, 1998, 2011 and 2019. The Revised Universal Soil Loss Equation (RUSLE) was implemented within a Geographic Information System (GIS) framework, incorporating five critical factors: rainfall erosivity (R), soil erodibility (K), topographic slope length and steepness (LS), land cover (C) and conservation practices (P). By interpreting these factors as proxies of hydrological processes—such as rainfall energy, runoff generation, infiltration capacity and hillslope hydrological connectivity—the analysis provides insight into how water-driven erosion mechanisms evolve under land use change. The results reveal significant changes in erosion rates strongly associated with land use transitions and climatic variability over the study period. Forested and pasture lands consistently exhibited lower erosion rates, whereas areas under annual crops and steep slopes were subject to markedly greater soil loss. A substantial increase in erosion was observed between 1986 and 1998 followed by a partial recovery by 2019, corresponding with a decline in agricultural land use and the expansion of forest and pasture areas. Furthermore, an erosion risk exposure map identified that 28.9% of the watershed—mainly in the eastern and upper watershed—remains highly vulnerable to erosion. These findings underscore the value of spatially explicit erosion modelling as a critical tool for informing sustainable land management and targeted soil conservation efforts in fragile tropical mountain landscapes. These findings demonstrate how shifts in hydrological processes—particularly runoff concentration, rainfall–runoff response and surface–vegetation interactions—mediate erosion dynamics over time. Overall, the study highlights how soil erosion modelling can improve understanding of hydrological functioning in tropical peri-urban landscapes and provide actionable information for integrated soil–water management.

Considering the intensified floods in the tropical river basins, this study assesses the climate change-induced flood risk accounting for the reservoir releases associated with crop damage and the monetary benefits from paddy cultivation. Using the three best-performing Global Climate Models (GCMs) out of nine, it analyzes the flood risk for agricultural production associated with a design flood in the typical Mahanadi River delta under a retrospective and six (2010s, 2040s and 2070s; and Representative Concentration Pathways (RCP): RCP4.5 and RCP8.5) projected scenarios. Subsequently, a probable flood adaptation strategy employing alternate rice planning in the near-future period and a selected GCM is proposed. It reveals an increased flood hazard in the mid-century followed by a decline towards the end of the century. Prolonged duration of low flood depth leads to very high crop vulnerability to floods in the projected periods under both RCP4.5 and RCP8.5 scenarios. While a little to moderate increase in overall flood risk is depicted by the MIROC-ESM-CHEM model-based predictions, the HadGEM2-AO and IPSL-CM5A-MR models indicate high flood risk in the future projected periods as compared to the historical episode. An alternate agricultural planning considering the net return from crop production can serve as a potential adaptation strategy dealing with the harsh effects of extreme floods in the river delta. The advocated methodology of flood risk assessment and adaptation using hydrodynamic flood modelling with consideration of reservoir releases is one of its kind and can be implemented in any world river basin.

Anthropogenic activities, particularly ecological and water conservancy projects, have profoundly altered land surfaces. However, quantifying their basin-scale hydrological impacts remains challenging. This study focused on the Qin River Basin (QRB), a major tributary in the ecologically sensitive middle reaches of the Yellow River where such projects are extensively implemented. Employing the Soil and Water Assessment Tool (SWAT) model, we quantified the impacts of the Returning Agricultural Land to Forest (RAF) and Returning Agricultural Land to River (RAR) projects on QRB hydrological processes from 2010 to 2018. Results indicated that the SWAT model performed robustly with Nash-Sutcliffe efficiency coefficients (NSE) of 0.70 to 0.72, determination coefficients (R²) of 0.71 to 0.79 and percent bias (PBIAS) below 11%. RAF implementation reduced total basin runoff by 3.00%, driven by increased surface runoff up to 3.89%, decreased lateral flow by 11.46%, and significantly increased groundwater flow by 2366.67%. Spatially, surface runoff increases concentrated in the northern basin and eastern tributaries, while lateral flow reductions were most severe in central regions. For RAR projects, hydrological responses scaled positively with agricultural-to-waterbody conversion area, showing 2.5-fold greater efficacy on slopes under 15° versus under 6°. Basin-wide runoff components increased proportionally to buffer width expansion, though spatial tradeoffs emerged: upper reaches exhibited surface runoff reduction from 1.29% to 21.74%, while lower reaches experienced groundwater depletion from 1.99% to 36.96% decrease. These findings highlight that spatial planning informed by slope conditions is vital for effective water resource management in semi-humid basins under intensive anthropogenic intervention.