Study on runoff simulation of the upstream of Minjiang River under future climate change scenarios

Climate change is one of the main factors that affect runoff changes. In the upstream of Minjiang River, the temperature increased significantly in the last 50 years, while the precipitation decreased on the contrary. In order to analyze the effect of climate change on site runoff, watershed runoff depth and evaporation, nine climate scenarios are assumed based on rainfall and temperature indicators. A SWAT model of Minjiang River is constructed, and runoff simulation is carried out with the nine scenarios. The results show that if precipitation increases or decreases 20 %, the change rate of runoff depth will increase or decrease 28–32 %; if temperature increases or decreases 2 °C, the change rate of runoff depth will decrease or increase 1–6 %; if temperature increases or decreases 2 °C, the change rate of the potential evaporation will increase or decrease 5–16 %, and the actual evaporation rate of variation will increase or decrease 1–6 %. Overall, precipitation variation has greater effect on simulated runoff than temperature variation dose. In addition, temperature variation has more obvious effect on the runoff simulation results in dry years than in wet years. The actual evaporation of watershed depends on evaporation capacity and precipitation and increases with the increasing of the potential evaporation and precipitation. The study also shows that the climate change scenarios analysis technology, combined with SWAT hydrological model, can effectively simulate the effect of climate change on runoff.     

Study on runoff simulation of the upstream of Minjiang River under future climate change scenarios

Climate change is one of the main factors that affect runoff changes. In the upstream of Minjiang River, the temperature increased significantly in the last 50 years, while the precipitation decreased on the contrary. In order to analyze the effect of climate change on site runoff, watershed runoff depth and evaporation, nine climate scenarios are assumed based on rainfall and temperature indicators. A SWAT model of Minjiang River is constructed, and runoff simulation is carried out with the nine scenarios. The results show that if precipitation increases or decreases 20 %, the change rate of runoff depth will increase or decrease 28–32 %; if temperature increases or decreases 2 °C, the change rate of runoff depth will decrease or increase 1–6 %; if temperature increases or decreases 2 °C, the change rate of the potential evaporation will increase or decrease 5–16 %, and the actual evaporation rate of variation will increase or decrease 1–6 %. Overall, precipitation variation has greater effect on simulated runoff than temperature variation dose. In addition, temperature variation has more obvious effect on the runoff simulation results in dry years than in wet years. The actual evaporation of watershed depends on evaporation capacity and precipitation and increases with the increasing of the potential evaporation and precipitation. The study also shows that the climate change scenarios analysis technology, combined with SWAT hydrological model, can effectively simulate the effect of climate change on runoff.

     

Coupling a glacier melt model to the Variable Infiltration Capacity (VIC) model for hydrological modeling in north-western China

For the sustainable utilization of rivers in the mid and downstream regions, it is essential that land surface hydrological processes are quantified in high cold mountains regions, as it is in these regions where most of the larger rivers in China acquire their headstreams. Glaciers are one of the most important water resources of north-west China. However, they are seldom explicitly considered within hydrological models, and climate-change effects on glaciers, permafrost and snow cover will have increasingly important consequences for runoff. In this study, an energy-balance ice-melt model was integrated within the Variable Infiltration Capacity (VIC) macroscale hydrological model. The extended VIC model was applied to simulate the hydrological processes in the Aksu River basin, a large mountainous and glaciered catchment in north-west China. The runoff components and their response to climate change were analyzed based on the simulated and observed data. The model showed an acceptable performance, and achieved an efficiency coefficient R ² ≈ 0.8 for the complete simulation period. The results indicate that a large proportion of the catchment runoff is derived from ice meltwater and snowmelt water. In addition, over the last 38 years, rising temperature caused an extension in the snow/ice melting period and a reduction in the seasonality signal of runoff. Due to teh increased precipitation runoff, the Aksu catchment annual runoff had a positive trend, increasing by about 40.00 × 10⁶ m³ per year, or 25.7 %.     

基于LSTM的青藏高原冻土区典型小流域径流模拟及预测

冻土覆盖率高的小流域的径流形成受温度因素控制明显,普通水文模型不适用,而常规冻土水文模型因需要较多的气象观测要素而难以应用。考虑冻土流域产流机制,利用青藏高原腹地风火山小流域2017—2018年逐日降水、气温、径流观测数据,以降水、气温为输入,径流为输出,基于长短期记忆神经网络（LSTM）建立了适用于小流域尺度的冻土水文模型,并利用2019年观测数据进行验证。模型得益于LSTM特殊的细胞状态和门结构能够学习、反映活动层冻融过程和土壤含水量变化,具有一定的冻土水文学意义,能很好地模拟冻土区径流过程。模型训练期R²、NSE均为0.93,RMSE为0.63 m³·s^-1,验证期R²、NSE分别为0.81、0.77,RMSE为0.69 m³·s^-1。同时,为了验证模型可靠性,将模型应用于邻近的沱沱河流域,模型训练期（1990—2009年）R²、NSE均为0.73,验证期（2010—2019年）R²、NSE分别为0.66、0.64,模拟结果较好。考虑到未来气候变化,通过模型对风火山流域径流进行了预测：降水每增加10%,年径流增加约12%;气温每升高0.5 ℃,年径流增加约1%;春季融化期、秋季冻结期径流增幅明显,而由于蒸发加剧、活动层加深,径流在8月出现了减少。模型经训练后依靠降水、气温作为输入能较好地模拟、预测青藏高原冻土区小流域径流,为缺少土壤温度、水分等观测数据的冻土小流域径流研究提供了一种简单有效并具有一定物理意义的方法。     

内陆河高寒山区流域分布式水热耦合模型（Ⅱ）：地面资料驱动结果

以黑河出山日平均流量作为对比，利用26个降水站点、11个气温站点和14个潜在蒸发站点2000年日资料，模型设计了6套气象因子空间分布方案，进行数值模拟试验，结果表明，在黑河流域现有观测站点的情况下，利用各种空间插值方法所得结果基本相当，考虑地面高程的三维插值与不考虑地面高程的二维插值结果相差不大，补充距离研究区较远的站点观测资料，模型结果反而变差。最终模型采用基于二维算法的最近距离法（nearest），利用2000年资料校正模型，计算与实测黑河日出山平均流量序列的效率系数为0.6101，平衡误差为0.0808％。以1999年资料验证模型，效率系数和平衡误差分别为0.6270和-2.9824％。模型基于水热连续方程模拟了黑河山区流域水热交换和耦合过程，探讨了流域的水量平衡，分析了水量平衡因子的时空分布，其模拟结果表明，内陆河高寒山区流域主要为浅表产流，高山草甸具有拦蓄降水和水源涵养作用，并反映了高山地区浅表土壤地下厚层冰的聚集过程。各种模型结果与本区野外实际调查结果基本一致，也符合当前对寒区流域水文循环过程的定性认识。     

东北半干旱地区流域分布式水文模拟——以洮儿河流域为例

以东北半干旱地区典型流域-洮儿河流域为研究对象,应用SWAT模型对流域水文过程进行了模拟研究;选择流域上游子流域和中下游子流域分别进行参数敏感性分析,识别出影响模拟结果的敏感参数,研究发现部分参数敏感性存在空间变异性,分析主要原因在于气候和下垫面的空间异质性导致了流域上下游产流模式存在差异。采用1988-1997年水文气象数据进行模型率定和验证,结果表明：干流水文站月流量过程率定期Nash-Sutcliffe 效率系数平均值为0.78,验证期为0.72,相关系数都达到0.86以上,水量误差大多在20%以内,对日过程的模拟也有较高的精度;枯水年模拟结果较差,主要是因为流域降水站数量不够,难以反映降水的时空分布。对于水文、气象等资料相对缺乏的东北半干旱地区,SWAT模型的模拟结果总体令人满意,可以应用于与流域径流相关的各种模拟分析,研究成果对进一步加强洮儿河流域水资源综合管理提供了依据和手段。     

气象产品的广义联合偏差修正方法及其应用

卫星气象产品、气候模式预测数据通常与地面观测数据存在偏差,为保证数据的可靠性和合理性,需要对其进行偏差校正,但偏差校正过程往往受具体区域气象特征、方法本身假定等因素的影响,导致修正效果不佳。为此,本文提出一种广义联合偏差修正方法,相较于现有研究最常用的单变量QM修正方法以及固定多变量修正顺序的JBC修正方法,该方法充分考虑到流域尺度降水和气温双变量的时空相关性,并结合其对径流的主导作用对变量修正顺序进行动态调整,实现了QM法和JBC法的优势互补。在澜沧江-湄公河流域的应用表明：考虑降水、气温相关性可显著改善降水和温度极值的修正效果,尤其是5、6月份,修正后气象与实测数据的纳什系数提升了0.5以上;考虑气象要素的修正次序显著降低了修正后的降水和温度频率分布及均值偏差;利用修正后的气象数据驱动分布式水文模型时,部分月份的径流模拟精度提升了54.3%。     

水文模型在估算冰川径流研究中的应用现状

冰川径流估算是气候变化风险评估和水资源可持续管理的重要内容.冰川径流估算方法主要包括:直接观测法、冰川物质平衡法、水量平衡方程法、水化学示踪法和水文模型法.本文首先对五种方法的应用情况进行简要总结,进而重点阐述水文模型法在估算冰川径流研究中的应用现状.水文模型法是冰川径流估算研究中使用最频繁的方法,使用方式主要包括耦合冰川模块和开发新的冰川水文模型.冰川水文模型中的消融算法主要包括温度指数模型(度日因子法)、修正的温度指数模型、能量平衡模型.受当前观测条件限制,修正的温度指数模型兼顾能量平衡模型和温度指数模型的优势而成为冰川水文模型中最流行的方法.随着学科的发展进步,能量平衡模型与水文模型的耦合将会成为未来的研究重点,发展大尺度分布式冰川水文模型是冰川水文学的未来发展方向之一.     

青藏高原兹格塘错流域50年来湖泊水量对气候变化响应的模拟研究

运用数值模拟建立青藏高原兹格塘错流域土壤、植被、气候等的空间和属性数据库;接着,借助分布式流域尺度水文模型（SWAT模型）,对兹格塘错1956—2006年间的流量进行模拟实验;最后,反演50年来兹格塘错流域水文过程,测试流域温度、降水和蒸发组合的敏感因子对湖泊水量变化的效应,探讨50年来湖泊水量对气候变化的响应。模拟实验的边界条件设置为自然地形、土壤、植被覆盖,其中土壤资料包括有机质含量、粒径等理化参数。模拟结果表明：兹格塘错的年平均流量为6.3m3/s,流量高峰集中在8月至10月,并且由于融雪补给的关系,3月出现另一个流量高峰;模拟结果与遥感解译所得到的结果吻合较好。敏感实验表明：兹格塘错流域内温度、降水和蒸发组合的敏感因子实验具有高原特征,即高原湖泊的水文过程和湖泊流量变化有着较为敏感的响应关系;兹格塘错流量受降水的影响最大,随着降水的增加,流量有所增加;在温度升高的情况下,流域蒸发量增加速度大,兹格塘错流量增加的效应不明显,而在冷湿模式下,流域蒸发量降低,兹格塘错流量增加显著。     

青藏高原土壤水热过程模拟研究(Ⅱ):土壤温度

模拟青藏高原土壤水分和热量迁移过程的连续变化对于全球变化研究具有非常重要的意义, 其准确模拟是提高陆面过程模拟精度的重要条件. 利用大尺度水文模型对沱沱河站点以1 h为步长, 共399 d的土壤温度模拟结果与观测结果的对比表明, 土壤中共11个不同深度的观测点的模拟温度总体的变化趋势与观测值一致, 可以进行长时间的模拟. 对于地表温度, 模拟的日变化幅度比实测的变化幅度大, 但均值一致, 原因在于模型的土壤参数中没有考虑有机质含量, 在计算能量平衡时需要增加该土壤参数. 对于土壤底部的土壤温度的连续模拟表明, 采用常数的土壤下界算法和倾斜的(damping)土壤下界算法均与观测值的变化具有一定的差别, 而常数的下界算法与观测值更为接近.     

基于HBV模型的太子河流域径流变化情景预估

以太子河流域为研究区域,采用HBV水文模型对流域的水文过程进行模拟,并选取RegCM4.4区域气候模式输出的平均气温和降水数据来驱动HBV水文模型,模拟逐日径流过程,分析RCP4.5排放情景下未来太子河流域径流的演变。结果表明,HBV水文模型在太子河流域模拟效果较好,率定期与验证期Nash效率系数与确定性系数均在0.60以上,模型基本模拟出了洪水对降水的响应过程。RCP4.5情景下,2021 2070年太子河流域年平均气温呈持续升温趋势,流域降水和年径流深度呈微弱减少趋势。相较于基准期,年径流深度将增多9.79%,夏季和秋季径流深度上升明显。径流分位数的变化表明,峰值极端径流和枯水极端径流均较基准期有不同程度的增多,未来太子河流域发生极端洪涝的可能性较高。     

Runoff Change in Taizihe River Basin Under Future Climate Change Based on HBV Model

Taking the Taizihe River Basin located in Liaoning Province as a study area, we applied HBV hydrological model to simulate the hydrological process of this river basin with the support of observed daily precipitation, mean temperature, hydrological data in Xiaolinzi hydrologic station, and global digital elevation model data from SRTM3, land utilization types, etc. According to the simulation results of daily runoff, the possible impact of future climate change on runoff was analyzed through forcing HBV model by RegCM4.4 dynamic downscaled climatic data. The results show that HBV model performed generally well for daily simulation of the Taizihe River Basin with Nash Sutcliffe coefficient and deterministic coefficient being all over 0.60 in the calibration period and validation period, and the response of flooding to precipitation were simulated better. This indicates the HBV model can be successfully applied to the Taizihe River Basin. Mean temperature will increase obviously with persistent rising trend by RegCM4.4 model in 2021-2070 under RCP4.5 scenario. Annual precipitation and runoff depth are expected to reduce a bit. Compared with the baseline period (1986-2005), annual runoff depth will increase by 9.79%. At the same time, the runoff depth will increase significantly in summer and autumn. The variation of runoff quantile indicates that both peak extreme runoff and dry extreme runoff will increase to different degrees than that in the baseline period. In the future, the Taizihe River Basin will be likely to experience extreme flooding.     

气候变化对陆地水循环影响研究的问题

简要地回顾了现存的由气候情景驱动水文模型研究气候变化对陆地水循环影响的方法。指出这种单向连接方法很难将气候变暖及人类活动引起的陆地水循环变化反馈给大气。这既影响对降雨的预测精度,又不能正确地描写陆地水循环的变化。近10年来气候学家对大气环流模型中陆面过程模型的改进以及水文气候学家对大尺度水文模型研究所取得的进展,展现了它们之间的互补性,以及未来用水文-气候耦合模型方法研究气候变化与人类活动对陆地水循环影响及水资源预测的可能性。     

气候变暖对长江源径流变化的影响分析

在气候变暖背景下, 20世纪60年代以来, 长江源区气温年和四季增温显著, 蒸发量、 径流量总体呈增加趋势; 进入21世纪后, 源区降水量呈增加趋势。沱沱河作为长江源区的主要径流, 以此为代表研究长江源区气候变暖对径流的影响具有重要的现实意义。利用1981 - 2015年沱沱河水文站径流量资料、 沱沱河同期气象站降水量、 气温、 蒸发量的实测资料, 分析了长江源区沱沱河降水、 气温、 蒸发量变化对径流量的影响。结果显示： 在全球变暖背景下, 近35 a来沱沱河流域年及四季平均气温、 平均最高气温、 最低气温均呈显著增加趋势; 年及春、 夏、 秋季降水量增加而冬季降水量减少; 春、 冬季蒸发量呈增加趋势, 年及夏、 秋季蒸发量呈减少趋势。沱沱河流域降水量是影响径流量大小的最主要的气候因子, 夏季降水量的增多与夏季径流量的增多关系密切, 年平均最低气温升高导致的冰川和积雪融水对径流量的影响次之, 蒸发量对径流量的影响明显低于前两者。     

祁连山葫芦沟流域高山寒漠带非冻结期水文特征

高山寒漠带是我国内陆河山区和我国多数大江、大河源头的主产流区之一. 由于缺乏系统观测数据及相关研究的支撑,当前国内外研究较为匮乏,高山寒漠带水文循环过程机理尚不清楚. 通过在黑河上游葫芦沟流域高山寒漠带试验点布设水文循环观测试验,分析了典型高山寒漠带非冻结期水文特征. 结果表明：高山寒漠试验点观测期(2009年6月7日-9月30日)的降水量为541.4 mm;蒸发皿的蒸发量为256.9 mm,桶式微型蒸渗仪(Micro-Lysimeter)的蒸发量为122.8 mm,平均蒸发量为1.1 mm·d^-1. 根据观测,高山寒漠带凝结水量也比较丰富,凝结水虽然没有直接参与高寒山区水文循环的产汇流过程,但它消耗了能量,抵消了部分太阳辐射,间接地参与了产汇流过程. 高山寒漠带小流域在观测期的平均径流深为461.2 mm. 根据降水梯度获取的流域平均降水量为639.1 mm,径流系数为0.72.     

Regional climate change and its effects on the runoff of Manas River,Xinjiang, China

The effects of climate change on annual runoff were analyzed on the basis of hydrologic and meteorological data for the past 50 years recorded by six meteorological stations and the Kenswatt Hydrological Station in the headstream of the Manas River watershed. The long-term trends of climate change and hydrological variations were determined in a nonparametric test, and the periodicities were determined employing the extrapolation method of periodic variance analysis. Subsequently, a periodicity-trend superposition model was used to predict future change. The results show that both the climate factors (temperature and precipitation) and runoff have increased considerably and have significant relations; the relation between temperature and runoff is the more significant. There is periodicity of 18 years in the change in annual runoff, and the primary periodicity of changes in temperature and precipitation is, respectively, 3 and 15 years. The runoff variations are affected by climate change in the headstream, but do not shift simultaneously with abrupt changes in temperature and precipitation in the headstream. There is a significant positive relationship in winter between the North Atlantic Oscillation (NAO) and runoff, while there are negative correlations annually and in summer for the runoff lagging the NAO by 1 year. The NAO has certain effects on climate change that are mainly due to atmospheric circulation in the Manas River Basin, and thus, the NAO affects the runoff.     

Analysis of the Influence of Climate and Vegetation Change on Runoff in the Middle and Upper Reaches of the Pearl River Basin Based on Budyko Hypothesis*

Runoff, which is a key component in the hydrological cycle, is mainly controlled by climate factors and land-surface elements in non-humid regions. The impacts of climate and vegetation changes on runoff based on Budyko hypothesis in the middle and upper reaches of the Pearl River Basin was analyzed in this article. First, the temporal trend of variables in the study area during 1981-2013 was examined by using the Mann-Kendall trend test with trend-free pre-whitening. Second, the relationship of the parameter n in Fu's equation with factors of climate and vegetation coverage was built to reveal the time-variation process of n. Finally, the effects of climatic factors and vegetation coverage on runoff were assessed by analyzing the sensitivity of runoff to each variable. It is found that average temperature (T), maximum temperature (T_max) and minimum temperature (T_min) in the study area present an increasing trend while runoff (Q), precipitation (P), wind speed (u₂) and relative humid (RH) present decreasing trend. The parameter n in Fu's equation is significantly related to both climatic factors (including precipitation (P), average temperature (T), relative humid (RH), sunshine duration (S), wind speed (u₂)) and vegetation coverage index (NDVI). In terms of sensitivity of Runoff (Q) to the variation of each climatic factors and NDVI in the middle and upper reaches of the Pearl River Basin, precipitation (P) and NDVI have the highest sensitivity, followed by other climatic factors. Additionally, the precipitation (P) reduction is the main driving factor to the decline in runoff, while vegetation coverage is another important factor. In general, climate change affects runoff not only by changing the hydrological inputs (precipitation (P) and potential evaporation (PET) but also by altering the watershed characteristics as represented by the parameter n, while the impacts of vegetation coverage on runoff are exerted mainly through the alteration of the watershed characteristics.     

祁连山老虎沟流域强消融期径流对气候变化的响应

为定量研究老虎沟流域径流对气候变化的响应,利用老虎沟流域1959年和2014年强消融期（7月）的气象、径流数据,分析了强消融期气温、降水、蒸发、冰川消融量、径流（流域的径流深）等的变化,进而探讨了老虎沟流域强消融期气温分布和降水形态、流域蒸发和冰川消融对径流的影响。结果表明：老虎沟流域2014年强消融期径流比1959年多159 mm,增加了49.67%。2014年7月平均气温较1959年升高0.38℃,最低气温升高1.34℃。1959年和2014年7月降水量相差较小;老虎沟流域强消融期日降水和日径流之间呈负相关,蒸发量的变化较小,流域内祁连山站的混合态降水比例减少23.01%,导致降水转化为径流的比例增大;起决定性作用的是正积温, 2014年7月较1959年的正积温高11.71℃·d,主要由于2~4℃的气温日数增多导致正积温增加,从而加剧冰川消融对径流的补给。     

Climatic causes of ecological and environmental variations in the source regions of the Yangtze and Yellow Rivers of China

In the source regions of the Yangtze and Yellow Rivers of China, glaciers, frozen ground, the hydrological system, and alpine vegetation have changed over the past decades years. Climatic causes of these variations have been analyzed using mean monthly air temperature and monthly precipitation between 1956 and 2000, and monthly evaporation from φ20 evaporation pans between 1961 and 1996. In the source region of the Yangtze River, lower temperature and plentiful precipitation during the 1960s and continuing into the early 1980s triggered a glacier advance that culminated in the early 1990s, while a robust temperature increase and precipitation decrease since 1986 has forced glaciers to retreat rapidly since 1995. Permafrost degradation is another consequence of the climatic warming. The variations in the hydrological system and alpine vegetation are controlled mainly by the climate during the warm season. Warmer and drier summer climate is the major cause of a degradation of the vegetation, desiccation of the high-cold marshland, a decrease in the areas and numbers of lakes and rivers in the middle and north source regions of the Yangtze and Yellow Rivers, and a reduction in surface runoff in the source region of the Yangtze River for the last 20 years. The causes of eco-environmental change in Dari area, near the outlet from the source area of the Yellow River, are different from those elsewhere in the study area. A noticeable reduction in runoff in the source region of the Yellow River and degradation of alpine vegetation in Dari area are closely related to the permafrost degradation resulting from climate warming.     

渭河上游典型小流域水文特征差异性分析

根据渭河流域两个典型小流域的实测水文和气象资料,分析了不同气候和下垫面条件的流域水文特征及其差异性.结果表明:清源河和牛谷河流域的年平均气温呈上升趋势,降水、径流、泥沙、降水径流系数均呈减少趋势;两个流域的降水、径流和泥沙历年变化不一致,1998-2013年清源河流域降水量相对牛谷河流域减少了8.6%,1993-2013年牛谷河的径流相对减少了21.4%,2000-2013年清源河的泥沙相对减少了24.0%;两个流域的面积、河长、海拔、植被覆盖率等流域特征值相对差在-29.4%~-4.5%之间,气温、降水等气候特征值相对差在-27.4%~16.7%之间,而径流特征值相差较大,相对差在-90.2%~-84.7%之间,泥沙特征差异性更大,相对差在292%~347%之间.对气候、下垫面和人类活动对水文要素的影响进行了研究,受人类活动的影响,清源河流域1996-2013年年径流减少11.6%,牛谷河流域1993-2006年年径流减少25.9%,2007-2013年再减少10.5%,研究人类活动的调水减沙效应,对流域综合治理、生态环境建设具有一定的指导意义.同时,充分利用不同小流域实测水文气象数据,分析水文气象要素的变化规律,可以为分布式水文模型研究和中小河流洪水预警预报提供重要依据.