Simulation of site-scale water fluxes in desert and natural oasis ecosystems of the arid region in Northwest China     

Mingjuan Xie  Geping Luo  Olaf Hellwich  Amaury Frankl  Wenqiang Zhang  Chunbo Chen  Chen Zhang  Philippe De Maeyer 《水文研究》2021,35(12):e14444

The study of water fluxes is important to better understand hydrological cycles in arid regions. Data-driven machine learning models have been recently applied to water flux simulation. Previous studies have built site-scale simulation models of water fluxes for individual sites separately, requiring a large amount of data from each site and significant computation time. For arid areas, there is no consensus as to the optimal model and variable selection method to simulate water fluxes. Using data from seven flux observation sites in the arid region of Northwest China, this study compared the performance of random forest (RF), support vector machine (SVM), back propagation neural network (BPNN), and multiple linear regression (MLR) models in simulating water fluxes. Additionally, the study investigated inter-annual and seasonal variation in water fluxes and the dominant drivers of this variation at different sites. A universal simulation model for water flux was built using the RF approach and key variables as determined by MLR, incorporating data from all sites. Model performance of the SVM algorithm (R² = 0.25–0.90) was slightly worse than that of the RF algorithm (R² = 0.41–0.91); the BPNN algorithm performed poorly in most cases (R² = 0.15–0.88). Similarly, the MLR results were limited and unreliable (R² = 0.00–0.66). Using the universal RF model, annual water fluxes were found to be much higher than the precipitation received at each site, and natural oases showed higher fluxes than desert ecosystems. Water fluxes were highest during the growing season (May–September) and lowest during the non-growing season (October–April). Furthermore, the dominant drivers of water flux variation were various among different sites, but the normalized difference vegetation index (NDVI), soil moisture and soil temperature were important at most sites. This study provides useful insights for simulating water fluxes in desert and oasis ecosystems, understanding patterns of variation and the underlying mechanisms. Besides, these results can make a contribution as the decision-making basis to the water management in desert and oasis ecosystems.  相似文献   

齐齐哈尔市地理国情分析与表达     

刘艳芳  方佳琳  焦利民  彭金金 《测绘与空间地理信息》2016,(3):5-8

以齐齐哈尔市为例,利用地理国情普查数据与统计年鉴数据,构建自然地表指数、地理区位指数、生态覆被指数,对齐齐哈尔市各县、区的地理国情进行综合分析和地图表达。结果表明,齐齐哈尔市的总体条件较好,但区域差异较大,自然地表条件与地理区位条件均以中部的齐齐哈尔市辖区为优,而生态覆被条件则以北部和西部地区为优。  相似文献   

地理国情普查外业调查与核查探讨     

袁宗福  董庆 《测绘与空间地理信息》2016,(11):188-191

地理国情普查主要是查清我国地形地貌、地表覆盖等自然和人文地理要素的现状和空间分布情况,建立普查成果数据库,为开展常态化的国情监测奠定基础。正确理解吉林省地理国情普查技术设计和作业指导书,以及国情普查的内容与指标,进行外业核查与遥感影像解译样本采集工作,为最终形成地理国情要素数据、地表覆盖分类数据和遥感影像解译样本数据库奠定基础。  相似文献   

准噶尔盆地油气源、油气分布与油气系统   总被引：1，自引：0，他引：1  

陈建平  王绪龙  邓春萍  梁狄刚  张越迁  赵喆  倪云燕  支东明  杨海波  王屿涛 《地质学报》2016,90(3):421-450

准噶尔盆地是中国西部典型的多旋回叠合盆地,发育有石炭系、二叠系、三叠系、侏罗系、白垩系和古近系6套烃源岩,同时存在6大类原油和3大类天然气,广泛分布于盆地不同地区。西北缘原油总体相似,碳同位素组成轻(δ~(13)C-29‰),胡萝卜烷、类异戊二烯烷烃、三环萜烷、伽马蜡烷丰富,甾烷以C_(28)、C_(29)为主,基本没有重排甾烷,为第二类原油,来源于二叠系湖相烃源岩。腹部绝大多数原油与西北缘原油相似,但胡萝卜烷、类异戊二烯烷烃、伽马蜡烷等有差异,来源于不同凹陷的二叠系湖相烃源岩;少量原油碳同位素组成重(δ~(13)C-28‰~-26‰),Pr/Ph大于2.5,三环萜烷以C_(19)、C_(20)为主,藿烷丰富而伽马蜡烷极低,以C_(29)规则甾烷及重排甾烷为主,为第四类原油,来源于侏罗系煤系烃源岩。东部存在5种类型原油,第一类原油碳同位素组成特别重(δ~(13)C-26‰),来源于石炭系烃源岩;第二类原油与腹部地区绝大多数原油十分相似,来源于二叠系湖相烃源岩;第三类原油碳同位索组成轻,重排甾烷、Ts、C_(29)Ts及C_(30)重排藿烷异常丰富,来源于中上三叠统湖相烃源岩;第四类原油源于侏罗系煤系烃源岩;混合类原油为二叠系、三叠系、侏罗系原油的混合,各自贡献平均分别为20%、15%和65%。南缘存在4类典型原油,为第二、第四、第五和第六类原油,其中第二、第四类分别源于二叠系和侏罗系;第五类原油碳同位素组成轻(δ~(13)C-29‰)、Pr/Ph1.0、伽马蜡烷丰富且有两个异构体、Ts、C_(29)Ts、C_(30)重排藿烷、C_(27)~C_(29)异胆甾烷及C_(30)甲基甾烷丰富,来源于白垩系湖相烃源岩;第六类原油主要为中低成熟原油,碳同位素组成δ~(13)C~28‰~-26‰,C_(27)、C_(28)、C_(29)甾烷呈"V"型分布,甲藻甾烷异常丰富,来源于古近系湖相烃源岩。准噶尔盆地天然气有油型气、混合气和煤型气,前两类主要来源于二叠系湖相烃源岩和石炭系海相烃源岩,煤型气主要来源于石炭系和侏罗系煤系烃源岩。不同类型油气分布与不同时代烃源灶具有良好对应关系:石炭系油气主要分布于陆东-五彩湾;二叠系油气主要分布于西北缘、腹部与东部;三叠系原油仅分布于东部;侏罗系原油主要分布于东部与南部;白垩系原油仅分布于南缘中部;古近系原油仅分布于南缘西部。按照盆地构造特征及不同时代烃源灶与油气关系,将准噶尔盆地划分为西部、中部、东部、南部及乌伦古5个油气系统及15个子油气系统。  相似文献   

Iodine budget in surface waters from Atacama: Natural and anthropogenic iodine sources revealed by halogen geochemistry and iodine-129 isotopes     

《Applied Geochemistry》2016

Iodine enrichment in the Atacama Desert of northern Chile is widespread and varies significantly between reservoirs, including nitrate-rich “caliche” soils, supergene Cu deposits and marine sedimentary rocks. Recent studies have suggested that groundwater has played a key role in the remobilization, transport and deposition of iodine in Atacama over scales of millions-of-years. However, and considering that natural waters are also anomalously enriched in iodine in the region, the relative source contributions of iodine in the waters and its extent of mixing remain unconstrained. In this study we provide new halogen data and isotopic ratios of iodine (¹²⁹I/I) in shallow seawater, rivers, salt lakes, cold and thermal spring water, rainwater and groundwater that help to constrain the relative influence of meteoric, marine and crustal sources in the Atacama waters. Iodine concentrations in surface and ground waters range between 0.35 μM and 26 μM in the Tarapacá region and between 0.25 μM and 48 μM in the Antofagasta region, and show strong enrichment when compared with seawater concentrations (I = ∼0.4 μM). In contrast, no bromine enrichment is detected (1.3–45.7 μM for Tarapacá and 1.7–87.4 μM for Antofagasta) relative to seawater (Br = ∼600 μM). These data, coupled to the high I/Cl and low Br/Cl ratios are indicative of an organic-rich sedimentary source (related with an “initial” fluid) that interacted with meteoric water to produce a mixed fluid, and preclude an exclusively seawater origin for iodine in Atacama natural waters. Iodine isotopic ratios (¹²⁹I/I) are consistent with halogen chemistry and confirm that most of the iodine present in natural waters derives from a deep initial fluid source (i.e., groundwater which has interacted with Jurassic marine basement), with variable influence of at least one atmospheric or meteoric source. Samples with the lowest isotopic ratios (¹²⁹I/I from ∼215 to ∼1000 × 10⁻¹⁵) strongly suggest mixing between the groundwater and iodine storage in organic-rich rocks (with variable influence of volcanic fluids) and pre-anthropogenic meteoric water, while samples with higher values (∼2000–93,700 × 10⁻¹⁵) indicate the input of anthropogenic meteoric fluid. Taking into account the geological, hydrologic and climatic features of the Atacama region, we propose that the mean contribution of anthropogenic ¹²⁹I is associated with ¹²⁹I releases during nuclear weapon tests carried out in the central Pacific Ocean until the mid 1990's (¹²⁹I/I = ∼12,000 × 10⁻¹⁵). This source reflects rapid redistribution of this radioisotope on a global scale. Our results support the notion of a long-lived continental iodine cycle in the hyperarid margin of western South America, which is driven by local hydrological and climate conditions, and confirm that groundwater was a key agent for iodine remobilization and formation of the extensive iodine-rich soils of Atacama.  相似文献   

松花江白山河段冰情数值计算及分析          下载免费PDF全文

樊霖  茅泽育  吴剑疆  齐文彪 《水科学进展》2016,27(6):890-897

根据水动力学、河流动力学、热力学、河冰水力学及固体力学等原理,针对松花江上游白山河段具体特征,建立了河冰数学模型,并应用有限差分计算方法,对白山河段冬季冰情演变进行了精确模拟。应用该河段1958-1973年共15年完整的地形、气象、水文、热力、冰情等原型观测资料,分别进行了模型参数率定及冰情数值模拟。研究结果表明:白山河段的封冻首先开始于白山坝址下游4 km的大崴子河段,然后封冻边缘逐渐上溯,最终到达松14断面;计算的白山河段冰花堆积体外形与河床纵剖面呈相似趋势;各种水力及冰情要素的数值计算结果和实测值吻合较好,所建立的数值模型能较好地模拟该河道的冰情。研究结果对东北地区河流冬季冰情研究及冰害防治具有一定的借鉴意义。  相似文献   

中国大陆降水时空变异规律——Ⅲ. 趋势变化原因          下载免费PDF全文

任国玉  柳艳菊  孙秀宝  张莉  任玉玉  徐影  张华  战云健  王涛  郭艳君  陈峪  唐国利  郭军 《水科学进展》2016,27(3):327-348

中国大陆现代降水表现出若干长期变化特征,对现代降水趋势性变化的原因,目前还没有很好了解。结合多种资料分析以及前人研究成果,对中国大陆近几十年降水变化趋势的原因进行了探讨,得到以下初步认识:① 现代降水量变化趋势具有明显的地域性差异,全国平均没有表现出显著增加或减少的长期变化,但强降水事件频率和降水量出现明显增多,而小雨事件特别是痕量降水事件显著减少。② 再分析资料表明,最近几十年全国水汽净收支量在一定程度上增加了,实际观测资料显示近地面和对流层中下层空气比湿或大气可降水量出现较明显上升趋势。③ 代用资料序列分析显示,全国大部地区近几十年降水变化仍处于晚近历史时期正常自然波动范围内;近百年观测的降水量序列也表明,黄淮海地区降水具有多重时间尺度相互叠加作用特点,低频自然气候变异的影响信号有清晰表现。④ 人类活动引起的大气中温室气体浓度增加对全国或东部季风区现代降水变化影响的信号,目前仍难以识别;区域性近地面风速减弱导致的雨量观测系统偏差以及大范围气溶胶浓度增加,可能是东部季风区大多数台站观测到的强降水事件频率增加和小雨频率显著减少的两个重要原因。⑤ 主要与城市化影响相关的地面观测资料系统偏差,可以部分解释现有分析表明的短历时强降水事件频率和累计降水量增加现象,同时也很可能是城市台站小雨和痕量降水事件频率明显下降的另一重要原因。  相似文献   

长兴岛碳酸盐岩裂隙岩溶水特征分析     

陈冶  程微  宋波  宋建伟  程静  孙丽萍 《化工矿产地质》2016,(2):79-84

长兴岛碳酸盐岩区占整个岛的44%,受降雨、岩性、构造等条件的影响,岩溶较发育,地下水资源较丰富,且水质较好,适宜作为饮用水水源。在收集大量基础地质资料,并结合现场调查、钻探、抽水试验成果,分析了从上至下5层岩溶带的发育特征、赋水性规律及补、径、排条件。同时考虑供水水文地质条件,进行了天然资源和开采资源概算,及成井条件、水质的分析评价。  相似文献   

山东省重要地质遗迹自然区划研究          下载免费PDF全文

蒙永辉  王集宁  于得芹 《山东国土资源》2016,32(2)

地质遗迹区划是地质遗迹资源保护的基础,该文根据山东省重要地质遗迹资源的空间分异和山东省大地构造二级构造单元,划分出3个地质遗迹大区,再以其自然分布规律、遗迹形成时间、空间、成因和地质构造单元的关联性进一步划分出8个地质遗迹区和24个地质遗迹集中区,从而建立了山东省重要地质遗迹自然区划系统,亦为地质遗迹保护提供了可靠的科学依据。  相似文献   

津冀海岸线现状、变化特征及保护建议   总被引：1，自引：0，他引：1  

施佩歆  王福  商志文  康慧  肖国强  杨吉龙  李建芬  姜兴钰  陈永胜  田立柱  李勇 《地质通报》2016,35(10):1630-1637

根据覆盖全区的3期遥感影像和实地调查,以及对滨海新区和滦河口2个典型区更深入的案例研究(包括回溯至1870年、1950年的基准岸线及逐年遥感信息),对津冀沿海海岸线现状进行解译和分类,并分析岸线变化特征及成因。津冀沿海现状岸线总长度894km,可以划分为自然岸线、半开发岸线和人工岸线3类,长度分别为90km、329km和475km。1950年以前为自然因素主导的岸线变化,1950年以后变为人类活动主导的岸线向海推进,逐渐加强的人类活动至2010年达到顶峰。在全球海面上升和区域地面下沉的大背景下,海岸线的自然演化趋势应该是向陆蚀退,但是人类活动主导的岸线变化却表现为违反自然趋势的向海推进。今后,向海推进最前沿的围海造陆区将受到来自海洋越来越强烈的影响,亟需加强监测和防护。兼顾环境保护与开发两方面的长远需求,建议赋予海岸线新的定义与内涵,划定岸线保护红线,恢复部分岸线的自然属性。  相似文献