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In frequency analysis of annual maximum flood series (AMFS), it is mechanism‐based and significant to incorporate the information of the underlying "ordinary" daily streamflow events for improving accuracy of flood risk estimation and appropriate management. In previous studies related to flood nonstationarity, the classical norming constants method (C‐NCM) has been used to derive statistical parameters of annual maximum flood distribution from daily streamflow distribution. However, C‐NCM does not flexibly consider the feasible range of the scale parameter of annual maximum flood distributions, which can result in the inability to provide sufficient and reliable models to fit AMFS. This paper aims to investigate the potential of two alternative norming constants methods in fitting annual maximum floods, namely the Hall's norming constants method (H‐NCM) and the Fisher and Tippetts' norming constants method (FT‐NCM) respectively. A comparative study of these three methods was carried out using hydrological streamflow series of 77 stations in the Yangtze and Yellow River basins, China. The results found that H‐NCM outperforms both C‐NCM and FT‐NCM for the stations with relatively low‐skewness coefficient of AMFS. Therefore, H‐NCM is recommended to prioritize for practical applications when considering daily streamflow rather than small samples of flood events. Furthermore, if the skewness coefficient exceeds Cs,Gumbel≈1.14, the overall modelling performance of these three methods is significantly deteriorated. This can provide some reference for the applicability of the norming constants method in flood frequency analysis. [ABSTRACT FROM AUTHOR]

Lake ice sublimation plays an important role in lake water budget, while there is huge uncertainty in estimation of lake ice sublimation and its proportion in annual lake total water vapor flux. In the present study, we investigated the annual total water vapor flux and ice sublimation at 15 frozen lakes or lake groups in China using three different methods, namely, the Community Land Model (CLM) simulations (Penman‐Monteith equation and pan observations) that considers (could not reflect) heat storage of lakes; the potential changes of lake total water vapor flux and ice sublimation with climate warming were also predicted. The results illustrate that the annual lake total water vapor flux obtained from Penman‐Monteith equation, pan observation, CLM simulation decreased in sequence, and ice sublimation obtained from pan observation, Penman‐Monteith equation, CLM simulation decreased in sequence. The lake ice sublimation from CLM occupied 7.4%–26.6% of corresponding annual lake total water vapor flux during 1950s–2010s in different regions of China. The ice sublimation and its proportion in lake total water vapor flux from these three methods were all highly correlated, with R2 being 0.86–0.97. The annual lake total water vapor flux will significantly increase in all frozen‐lake regions in China with the climate warming. Climate warming potentially reduce sublimation at most lakes. Key Points: Community Land Model (CLM) method is more accurate than pan and P‐M methods in calculating lake ice sublimationIce sublimation from CLM occupied 7.4%–26.6% of lake total water vapor fluxAnnual lake total water vapor flux will significantly increase in China with climate warming [ABSTRACT FROM AUTHOR]

A least-square solver is presented for groundwater flux estimation using the one-dimensional conduction–advection equation, which was numerically solved using the MacCormack scheme. This approach was utilized to estimate groundwater fluxes from observed borehole temperatures under conditions of surface warming in both rural and urban areas in Leizhou Peninsula, China. The estimated groundwater recharge rate is 0.423 m/year, while the discharge rate is 0.269 m/year. The groundwater recharge rates were obtained in the north part of the study area, and the discharge locations were on Nansan, Donghai and Luzhou Islands, which fit favorably with the regional groundwater flow pattern. Relatively high correlations and low root mean square errors were detected between observed and computed borehole temperature–depth profiles, indicating the estimation is reasonable. The misfit between the observed and computed data might be associated with the uneven distribution of ground surface temperature (GST) and vertical soil heterogeneity. The urban heat island effect contributes an increment of 0.006 °C per year to the GST in the study area, which induces a 0.96 °C higher subsurface temperature in both recharge and discharge areas. The utilization of surface air temperature (SAT) as the upper boundary might underestimate groundwater fluxes, which might lead to inaccurate information for regional groundwater resource management. [ABSTRACT FROM AUTHOR]

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Summary: Rainwater percolation into bedrock and the contribution of bedrock groundwater flow to streamflow have been reported for several experimental catchments in China, Japan and the US. On the basis of previous studies, the particular runoff characteristics of granitic catchments were determined: (i) fast rainwater infiltration, (ii) obviously saturated throughflow (interflow) at the soil–bedrock interface, and (iii) obvious rainwater percolation into the bedrock and a substantial contribution of bedrock groundwater flow to streamflow. Next, the runoff generation characteristics of a small granitic catchment (0.99km2) in southern China were analyzed, based on long-term monitoring of rainfall, runoff at the catchment outlet and at different depths in two plots, along with monitoring of soil suction and soil water content at different depths in these two plots (5m×10m). According to the monitoring results, the maximum soil infiltration rate in this granitic catchment was larger than 4.45×10−4 m/s. Interflow was found at the soil–bedrock interface in plot B with a soil depth ⩽1m. In plot A overlain by a thick soil layer ⩾2m, interflow was mainly generated within an aquitard at a shallow depth (∼1m). The plot interflow hydrograph was similar, but slightly slimmer and sharper, than that of streamflow, illustrating that interflow is the main source of catchment streamflow at the storm scale. A semi-distributed model was constructed based on a digital elevation model, and the ratio of rainwater percolation into bedrock to precipitation in the study catchment from 1 April 2007 to 31 March 2008 was 0.33–0.47, in agreement with results for other granitic catchments. These results can aid in understanding the particular runoff generation characteristics of granitic catchments. [ABSTRACT FROM AUTHOR]