渭河流域气候变化与人类活动对径流的影响

以黄河最大的一级支流渭河为研究对象,根据渭河流域华县水文站1958--2011年径流资料,采用Mann—Kendall趋势检验、Pettitt非参数统计和双累积曲线法分析径流序列的变化趋势和突变点,同时采用水量平衡法定量分析气候变化和人类活动对径流量的影响。结果表明：1）华县水文站径流量呈显著下降趋势（标准正态统计变量〈-2．23）,年均递减系数为0．86mm／a;2）径流量自1994年呈显著性减少趋势,据此将径流序列划分为2个阶段,即基准期1958--1994年和变化期1995—2011年;3）变化期较基准期在枯水年、平水年和丰水年径流量分别下降64．6％、41．3％和45．5％,枯水年流量下降趋势最为明显;4）华县站以上控制区内降雨变化和人类活动对径流变化的贡献率分别为49．0％和51．0％,气候变化对渭河径流量的影响主要是由降水量的减少引起的。     

Response of hydrological drought to meteorological drought in the eastern Mediterranean Basin of Turkey

The hydrographic eastern Mediterranean Basin of Turkey is a drought sensitive area. The basin is an important agricultural area and it is necessary to determine the extent of extreme regional climatic changes as they occur in this basin. Pearson's correlation coefficient was used to show the correlation between standardized precipitation index(SPI) and standardized streamflow index(SSI) values on different time scales. Data from five meteorological stations and seven stream gauging stations in four sub-basins of the eastern Mediterranean Basin were analyzed over the period from 1967 to 2017. The correlation between SSI and SPI indicated that in response to meteorological drought, hydrological drought experiences a one-year delay then occurs in the following year. This is more evident at all stations from the mid-1990 s. The main factor causing hydrological drought is prolonged low precipitation or the presence of a particularly dry year. Results showed that over a long period(12 months), hydrological drought is longer and more severe in the upper part than the lower part of the sub-basins. According to SPI-12 values, an uninterrupted drought period is observed from 2002–2003 to 2008–2009. Results indicated that among the drought events, moderate drought is the most common on all timescales in all sub-basins during the past 51 years. Long-term dry periods with moderate and severe droughts are observed for up to 10 years or more since the late 1990 s, especially in the upper part of the sub-basins. As precipitation increases in late autumn and early winter, the stream flow also increases and thus the highest and most positive correlation values(0.26–0.54) are found in January. Correlation values(ranging between –0.11 and –0.01) are weaker and negative in summer and autumn due to low rainfall. This is more evident at all stations in September. The relation between hydrological and meteorological droughts is more evident, with the correlation values above 0.50 on longer timescales(12-and 24-months). The results presented in this study allow an understanding of the characteristics of drought events and are instructive for overcoming drought. This will facilitate the development of strategies for the appropriate management of water resources in the eastern Mediterranean Basin, which has a high agricultural potential.     

Budyko-Fu模型下气候季节性指标中水热变化时相差的选取研究

流域水热耦合过程研究中，Budyko理论近年来得到了广泛的应用，其中又以傅抱璞公式（Budyko-Fu）比较著名。本研究在Budyko-Fu模型下，对其控制性参数ω与3种气候季节性指标的关系分别进行了分析。3种气候季节性指标包括SI1—考虑年内月降水量距平特征，SI2—考虑用正弦曲线模拟降水量与潜在蒸散季节变化时各自的振幅差别特征，以及SAI—在SI2的基础上进一步考虑降水量与潜在蒸散季节变化的相位差别。文章探讨了SAI指标计算中降水量与潜在蒸散季节相位取值年际变化与否的影响，由此形成SAI1和SAI2两个指标；随后比较了不同气候季节性指标在径流变化模拟中的应用效果。结果表明，在流域尺度水热耦合年际过程分析中，若气候季节性指标采用SAI2，即同一流域水热变化时相差由多年平均状况确定，且年际间保持不变，则效果较好；由此季节性指标结合NDVI数据给出的参数ω半经验公式的决定系数（R²）达到了0.746。在此基础上应用Budyko-Fu公式，流域年径流量的模拟精度显著提高。     

关中地区主要河流丰枯变化特征分析

为了揭示关中地区主要河流天然径流系列丰枯状态及其变化规律,研究结合游程理论、Markov过程和时间序列方法,对关中地区渭河干流及其十余条重要支流的丰枯变化进行了系统分析。结果表明:偏枯状态是关中地区河流的主要状态,大多数河流的单独丰水概率要比单独枯水概率大,而多年连续枯水游程概率大于连续丰水概率,即关中河流较易发生单独丰水年和连续干旱年。这些表明关中地区河流的径流变化大,旱涝并存且干旱缺水问题相对突出。     

Reconstruction of hydrological changes based on tree-ring data of the Haba River,northwestern China

Reconstructing the hydrological change based on dendrohydrological data has important implications for understanding the dynamic distribution and evolution pattern of a given river. The widespread, long-living coniferous forests on the Altay Mountains provide a good example for carrying out the dendrohydrological studies. In this study, a regional composite tree-ring width chronology developed by Larix sibirica Ledeb. and Picea obovata Ledeb. was used to reconstruct a 301-year annual(from preceding July to succeeding June) streamflow for the Haba River, which originates in the southern Altay Mountains, Xinjiang, China. Results indicated that the reconstructed streamflow series and the observations were fitting well, and explained 47.5% of the variation in the observed streamflow of 1957–2008. Moreover, floods and droughts in 1949–2000 were precisely captured by the streamflow reconstruction. Based on the frequencies of the wettest/driest years and decades, we identified the 19 th century as the century with the largest occurrence of hydrological fluctuations for the last 300 years. After applying a 21-year moving average, we found five wet(1724–1758, 1780–1810, 1822–1853, 1931–1967, and 1986–2004) and four dry(1759–1779, 1811–1821, 1854–1930, and 1968–1985) periods in the streamflow reconstruction. Furthermore, four periods(1770–1796, 1816–1836, 1884–1949, and 1973–1997) identified by the streamflow series had an obvious increasing trend. The increasing trend of streamflow since the 1970s was the biggest in the last 300 years and coincided with the recent warming-wetting trend in northwestern China. A significant correlation between streamflow and precipitation in the Altay Mountains indicated that the streamflow reconstruction contained not only local, but also broad-scale, hydro-climatic signals. The 24-year, 12-year, and 2.2–4.5-year cycles of the reconstruction revealed that the streamflow variability of the Haba River may be influenced by solar activity and the atmosphere–ocean system.     

西北干旱区近50年气候变化对出山径流的影响分析——以黑河流域为例

对黑河上游山区1956—2004a祁连站气温与降水数据、莺落峡水文站出山径流进行各季年均值变化分析、基于MathCAD对气温和降水分别与出山径流的关系进行相关分析,发现近50a黑河流域气温与降水的变化没有显著的相关性,降水变化与径流的变化表现出正相关,而气温与径流则没有相关性。近50a降水各季变化没有一致性,却出现一定的规律,即春季持平,夏秋下降,而冬季增加。相对于降水而言,气温变化则表现出各季之间的一致性趋势,即近10a表现出明显的增温趋势,而且增温幅度相似,都在2℃左右。另外对气温与降水对出山径流的影响做了量化,降水与径流的相关系数为0.557,而气温与径流的相关系数只有0.045左右;根据影响径流的气候因子所占权重,集成气候(无量纲)变化曲线,显示出与径流变化的一致性,即气候变化对径流变化有明显的影响;依据本文分析和总结,预计今后10—20a气温、降水都将有升高或增加趋势,届时出山径流将相应增加。     

利用DAWAST模型推求雅鲁河流域日径流

本文利用DAWAST模型对雅鲁河流域实测日径流进行了模拟。     

黄土高原森林/非森林流域径流稳定性及其演变趋势对比

采用集中期、集中度等方法及M-K,Pettitt等非参检验法对比分析了黄土高原北洛河子午岭森林流域与相邻丘陵沟壑区非森林流域近50 a来的径流稳定性差异及演变趋势,为黄土高原地区生态治理的水文效应分析提供参考和借鉴.结果表明,黄土高原子午岭林区和非林区流域径流量年际尺度分布表现出一致的强变异性,年内分布均为双峰型特征,但林区峰型平缓,非林区陡峭.林区流域年内分布较非林区流域均匀,前者径流集中期较后者滞后1个月.近50 a来林区流域径流量无明显变化趋势,而非林区流域年、夏、秋及汛期径流量表现出显著性减少趋势,且有显著的跃变时间.无论径流过程或径流量年变化如何,林区稳定性要明显优于非林区流域.非林区流域的生态环境仍需要长时期的建设和维护.     

Monthly and seasonal streamflow forecasting of large dryland catchments in Brazil

Streamflow forecasting in drylands is challenging.Data are scarce,catchments are highly humanmodified and streamflow exhibits strong nonlinear responses to rainfall.The goal of this study was to evaluate the monthly and seasonal streamflow forecasting in two large catchments in the Jaguaribe River Basin in the Brazilian semi-arid area.We adopted four different lead times:one month ahead for monthly scale and two,three and four months ahead for seasonal scale.The gaps of the historic streamflow series were filled up by using rainfall-runoff modelling.Then,time series model techniques were applied,i.e.,the locally constant,the locally averaged,the k-nearest-neighbours algorithm(k-NN)and the autoregressive(AR)model.The criterion of reliability of the validation results is that the forecast is more skillful than streamflow climatology.Our approach outperformed the streamflow climatology for all monthly streamflows.On average,the former was 25%better than the latter.The seasonal streamflow forecasting(SSF)was also reliable(on average,20%better than the climatology),failing slightly only for the high flow season of one catchment(6%worse than the climatology).Considering an uncertainty envelope(probabilistic forecasting),which was considerably narrower than the data standard deviation,the streamflow forecasting performance increased by about 50%at both scales.The forecast errors were mainly driven by the streamflow intra-seasonality at monthly scale,while they were by the forecast lead time at seasonal scale.The best-fit and worst-fit time series model were the k-NN approach and the AR model,respectively.The rainfall-runoff modelling outputs played an important role in improving streamflow forecasting for one streamgauge that showed 35%of data gaps.The developed data-driven approach is mathematical and computationally very simple,demands few resources to accomplish its operational implementation and is applicable to other dryland watersheds.Our findings may be part of drought forecasting systems and potentially help allocating water months in advance.Moreover,the developed strategy can serve as a baseline for more complex streamflow forecast systems.     

RESENSIES—REVIEWS

Results at harvesting are described of two comprehensive NPK fertilizer experiments with E. grandis on sites previously under wattle in the Natal Midlands. The experimental sites differ considerably in respect of physiography, climate, and soil. The difference in climate and soil are clearly evident from the respective analyses of soil samples from the sites, one soil of a dystrophic series belonging to the Griffin form, and the other a mesotrophic series of the Hutton form.

Except in one instance, nitrogen application showed no significant response, which is expected on these nitrogen-enriched soils of old wattle plantations. There is a tendency, which in one instance was significant, that nitrogen has a depressive effect on E. grandis, but this is ascribed to burning the transplants when the fertilizer is too concentrated and applied too close to the trees.

Superphosphate application on these sites gives highly profitable results, the additional net profit per ha being nearly R400 on the better site and at least R35 on the poorer site. The optimum application rate on the better site is not more than 130 g superphosphate (8,3% P) per tree, while the optimum rate on the poorer site might be as high as 260 g.

Significant responses to potash application are limited to mesotrophic soils and are of a curvilinear nature. This last phenomenon especially is difficult to explain, but is known to have occurred elsewhere.