Analysis of Water Resources Supply and Demand and Security of Water Resources Development in Irrigation Regions of the Middle Reaches of the Heihe River Basin, Northwest China

Based on the data for meteorology, hydrology, soil, planting, vegetation, and socio-economic development of the irrigation region in the middle reaches of the Heihe River basin, Northwest China, the model of balance of water supply and demand in the region was established, and the security of water resource was assessed, from which the results that the effects of unified management of water resources in the Heihe River basin between Gansu Province and Inner Mongolia on regional hydrology are significant with a decrease in water supply diverted from Heihe River and an increase in groundwater extracted. In addition, it was found that the groundwater level has been steadily decreasing due to over pumping and decrease in recharges. In present year （2003）, the volume of potential groundwater in the irrigation districts is far small because of the groundwater overdraft; even in the particular regions, there is no availability of groundwater resources for use. By 2003, water supply is not sufficient to meet the water demand in the different irrigation districts, the sustainable development and utilization of water resources are not secured, and the water supply crisis occurs in Pingchuan irrigation district. Achieving water security for the sustainable development of society, agriculture, economy, industry, and livelihoods while maintaining or improving the abilities of the management and planning of water resources, determining of the reasonable percentage between water supply and groundwater utilization and water saving in agricultural irrigation are taken into account. If this does not occur, it is feared that the present performance of water development and planning may further aggravate the problem of scarcities of water resources and further damage the fragile ecological system.

Tree-ring-based reconstruction of temperature variability(1445–2011) for the upper reaches of the Heihe River Basin, Northwest China

Long-term temperature variability has significant effects on runoff into the upper reaches of inland rivers. This paper developed a tree-ring chronology of Qilian juniper (Sabina przewalskii Kom.) from the upper tree-line of the middle Qilian Mountains within the upper reaches of Heihe River Basin, Northwest China for a long-term reconstruction of temperature at the study site. In this paper, tree-ring chronology was used to examine climate-growth associations considering local climate data obtained from Qilian Meteorological Station. The results showed that temperatures correlated extremely well with standardized growth indices of trees (r=0.564, P<0.001). Tree-ring chronology was highest correlated with annual mean temperature (r=0.641, P<0.0001). Annual mean temperature which spans the period of 1445–2011 was reconstructed and explained 57.8% of the inter-annual to decadal temperature variance at the regional scale for the period 1961–2011. Spatial correlation patterns revealed that reconstructed temperature data and gridded temperature data had a significant correlation on a regional scale, indicating that the reconstruction represents climatic variations for an extended area surrounding the sampling sites. Analysis of the temperature reconstruction indicated that major cold periods occurred during the periods of 1450s–1480s, 1590s–1770s, 1810s–1890s, 1920s–1940s, and 1960s–1970s. Warm intervals occurred during 1490s–1580s, 1780s–1800s, 1900s–1910s, 1950s, and 1980s to present. The coldest 100-year and decadal periods occurred from 1490s–1580s and 1780s–1800s, respectively, while the warmest 100 years within the studied time period was the 20th century. Colder events and intervals coincided with wet or moist conditions in and near the study region. The reconstructed temperature agreed well with other temperature series reconstructed across the surrounding areas, demonstrating that this reconstructed temperature could be used to evaluate regional climate change. Compared to the tree-ring reconstructed temperature from nearby regions and records of glacier fluctuations from the surrounding high mountains, this reconstruction was reliable, and could aid in the evaluation of regional climate variability. Spectral analyses suggested that the reconstructed annual mean temperature variation may be related to large-scale atmospheric–oceanic variability such as the solar activity, Pacific Decadal Oscillation (PDO) and El Ni?o–Southern Oscillation (ENSO).

Water accounting for conjunctive groundwater and surface water irrigation sources: A case study in the middle Heihe River Basin of arid northwestern China

Oases in arid northwestern China play a significant role in the region＇s economic stability and development. Overex- ploitation of the region＇s water resources has led to serious environmental consequences. In oases, irrigated agriculture is the primary consumer of water, but water shortages resulting from dramatically growing human needs have become a bottleneck for regional sustainable development, making effective management of the limited available water critical. Effective strategies must be formulated to increase agricultural productivity while reducing its environmental impacts. To support the development of such strategies, water use patterns were analyzed during the 2007 and 2008 growing seasons, from May to early October, to identify opportunities for improving water management using the Mold- en-Sakthivadivel water-accounting method, which combines groundwater and surface water into a single domain and can provide a good estimate of the uses, depletion, and productivity of water in a water basin context. The study area lies in Linze County, Gansu Province, China. In the study area, the inflow water resources consist of irrigation, precipita- tion, and soil water, which accounted for 89.3%, 8.9%, and 1.8% of the total in 2007, and 89.3%, 4.8%, and 5.9% in 2008, respectively. The irrigation depends heavily on groundwater, which accounted for 82.1% and 83.6% of the total irrigation water in 2007 and 2008, respectively. In 2007 and 2008, deep percolation accounted for 50.1% and 47.9% of the water outflow, respectively, with corresponding depleted fractions of 0.51 and 0.55, respectively. For the irrigation district as a whole, the water productivity was only 1.37 CNY/m^3. To significantly increase crop water productivity and prevent depletion of the region＇s groundwater aquifer, it will be necessary to reduce the amount of water used for ir- rigation. Several water-saving agricultural practices are discussed and recommended.

Relationship between sand-dust weather and water dynamics of desert areas in the middle reaches of Heihe River

Sand-dust weather has become an international social-environmental issue of common concern, and constitutes a serious threat to human lives and economic development. In order to explore the responses of natural desert sand and dust to the dynamics of water in desertification, we extracted long-term monitoring data related to precipitation, soil water, groundwater, and sand-dust weather. These data originated from the test stations for desertification control in desert areas of the middle reaches of the Heihe River. We used an algorithm of characteristic parameters, correlations, and multiple regression analysis to establish a regression model for the duration of sand-dust weather. The response char-acteristics of the natural desert sand and dust and changes of the water inter-annual and annual variance were also examined. Our results showed： （1） From 2006 to 2014 the frequency, duration, and volatility trends of sand-dust weather obviously increased, but the change amplitudes of precipitation, soil water, and groundwater level grew smaller. （2） In the vegetative growth seasons from March to November, the annual variance rates of the soil moisture content in each of four studied layers of soil samples were similar, and the changes in the frequency and duration of sand-dust weather were similar. （3） Our new regression equation for the duration of sand-dust weather passed the R test, F test, and t test. By this regression model we could predict the duration of sand-dust weather with an accuracy of 42.9%. This study can thus provide technological support and reference data for water resource management and re-search regarding sand-dust weather mechanisms.

LAND DESERTIFICATION(DEGRADATION) AND ITS CONTROL IN LOWER REACH REGION OF HEIHE RIVER

The lower reach of Heihe River, also known as Ejina River, was called Ruoshui Riverin ancient times. This area, although fallen into extremely arid temperate desert in the EjinaBanner, Inner Mongolia, has been a main line of communication since then and formed thefertile Ejina Oasis relying on the water source flowing from the Qilian mountains. However,in the recent years the land desertification (degradation) in this area has developed rapidly,

Zircon U-Pb dating and Lu-Hf isotope study of intermediate-mafic sub-volcanic and intrusive rocks in the Lishui Basin in the middle and lower reaches of Yangtze River

Eight Mesozoic sub-volcanic and intrusive rocks in the Lishui Basin have been selected for zircon U-Pb dating and Lu-Hf isotopic analysis. The Laohutou, Datongshan,Daweizhuang, Yeshanao, Yanwaqiao, Xibeishan, Changshantou and Jianshan porphyrites yield concordant early Cretaceous ages of 130.5 ± 1.6 Ma, 136.0 ± 3.4 Ma, 132.7 ±2.7 Ma, 127.0 ± 1.9 Ma, 129.4 ± 1.7 Ma, 133.2 ± 2.1 Ma,131.1 ± 2.3 Ma and 127.4 ± 1.8 Ma, respectively. Zircon eHf(t) values for these rocks range from-3.54 to-9.11, mostly between-3.54 and-5.93, suggesting sources similar to those for coeval igneous rocks in other volcanic basins along the middle and lower reaches of Yangtze River. Considering the geochemical characteristics of coeval magmatic rocks in the middle and lower reaches of Yangtze River and its adjacent areas, this paper proposes a model of slab rollback to explain the Mesozoic magmatism in the east-central part of China continent. In the middle-late Jurassic to early Cretaceous(170–135 Ma), the Pacific plate started to subduct beneath the Eurasian continent, producing a compressive tectonic setting,and magmatism progressed from coast to the inland. The magmas of this period were derived mostly from partial melting of ancient crust. After *135 Ma, the subduction weakened, and the rollback of the subducted Pacific plate produced an extensional environment. This led to the formation of volcanic basins, the partial melting of enriched mantle sources and less ancient crust, and the intrusion of voluminous intermediate-mafic igneous rocks.

Measurement on the Harmony Coefficient of Agro-eco-economic System in the Arid Region

On the basis of the present research progress of ecological agriculture,we take Minle County and Linze County located in the middle reaches of Heihe River as the typical research units.Based on the rural social and economic data during the period of 2000-2010,theory and method of mathematical statistics are used to establish the measure theory and model of agro-eco-economic system harmony coefficient,including efficacy function,function of harmony coefficient,harmony coefficient and level of harmony coefficient.Based on the actual situation of research region,evaluation indicator system of agro-eco-economic system is established and measurement is carried out.Results show that the regional agro-eco-economic system in research region was in a serious imbalance in 2000-2013.The harmony coefficient of Minle showed a slight rise from 2000 to 2004,and then presented a fluctuating decline.Its rank of harmony coefficient experienced serious imbalance-extreme imbalance-moderate imbalance-low imbalance-serious imbalance-high imbalance.At the same time,the similar tendency happened in Linze County.The measuring results of subsystem in 2000-2013 further indicated that except that the harmony coefficient of economic subsystem in Minle County and Linze County was moderate and high,the ecological subsystem was at Level II and Level III,and social subsystem was at Level IV and Level III,in high and low imbalance status.Finally,several recommendations were put forward for optimizing agro-eco-economic system.

黑河中游绿洲边缘三种景观类型土壤水分动态特征及影响因素

土壤水分对干旱区旱生植物的生长发育必不可少,决定了旱生植物群落的演替动态和方向。探究黑河中游绿洲边缘不同景观类型的土壤水分动态特征,制定切实有效、科学合理的防风固沙措施,对于阻止荒漠化进程显得尤为重要。本文以黑河中游绿洲边缘的防护林、荒漠-绿洲过渡带和荒漠三种景观类型为研究对象,采用HYDRUS-2D模型模拟、LSD分析法、Pearson相关性分析等方法,研究三种不同景观类型土壤水分动态特征及影响因素。结果表明:(1)土壤体积含水量的RMSE为0.002~0.006 cm^(3)·cm^(-3),MRE为4.22%~5.20%,R^(2)为0.725~0.967,模拟结果与实测数据具有较高的吻合度,HYDRUS-2D模型可用于本研究区土壤水分动态的模拟研究。(2)防护林和荒漠-绿洲过渡带景观的土壤体积含水量随土层深度增加呈现出先增大后减小的变化趋势,荒漠景观则呈现出先减小后增大的变化趋势。(3)有效降水对土壤体积含水量动态变化起决定性作用,9.5 mm以上的降水量可以在短期内显著提高土壤水分含量和入渗深度,荒漠景观降水后的各时段土壤水分入渗深度高于防护林景观和荒漠-绿洲过渡带景观。(4)三种景观类型的土壤体积含水量与降水、蒸散发、容重、土壤颗粒组成、土壤持水性能等因素有关,且表现出不同程度的显著相关(P<0.01),其中,降水、黏粉粒含量与土壤体积含水量呈显著正相关,容重、砂粒含量与土壤体积含水量呈显著负相关性。因此,研究区栽植防风固沙灌木可以增加土壤黏粉粒含量,提高土壤收集利用雨水的能力,减缓入渗作用的进程,从而对土壤持水性能产生积极影响。

Assessing the evolution of oases in arid regions by reconstructing their historic spatio-temporal distribution： a case study of the Heihe River Basin, China

Oasis evolution, one of the most obvious surface processes in arid regions, affects various aspects of the regional environment, such as hydrological processes, ecological conditions, and microclimates. In this paper, the historical spatio-temporal evolution of the cultivated oases in the Heihe River Basin, the second largest inland watershed in the northwest of China, was assessed using multidisciplinary methods and data from multiple sources, including historical literature, ancient sites, maps and remotely sensed images. The findings show that cultivated oases were first developed on a large scale during the Han Dynasty （121 BC-220） and then gradually decreased in extent from the Six Dynasties period （220-581） to the Sui- Tang period （581-907）, reaching a minimum in the Song- Yuan period （960-1368）. An abrupt revival occurred during the Ming Dynasty （1368-1644） and continued through the Qing Dynasty （1644-1911）, and during the period of the Republic of China （1912-1949）, oasis development reached its greatest peak of the entire historical period. The oasis areas during seven major historical periods, i.e., Hart, Six Dynasties, Sui-Tang, Song-Yuan, Ming, Qing, and Republic of China, are estimated to have been 1703 kma, 1115 km2, 629 km2, 614 km2, 964 km2, 1205 km2, and 1917 km2, respectively. The spatial distribution generally exhibited a continuous sprawl process, with the center of the oases moving gradually from the downstream region to the middle and even upstream regions. The oases along the main river remained stable during most periods, whereas those close to the terminal reaches were subject to frequent variations and even abandonment. Socio-economic factors were the main forces driving the evolution of cultivated oases in the area; among them, political and societal stability, national defense, agricultural policy, population, and technological progress were the most important.

黄河流域中游地下水干旱演变规律及其对植被变化的响应

【目的】明确黄河流域中游地下水干旱时空演变规律。【方法】基于GRACE/GRACE-FO卫星数据和GLDAS数据计算标准化地下水干旱指数SGDI,利用改进的Mann-Kendall趋势检验研究和识别黄河流域中游的地下水干旱时空演变规律,利用Spearman相关分析研究地下水干旱对植被变化的响应。【结果】①黄河流域中游地下水储量异常以-0.027mm/d的速率变化,时空分布极不均匀。②地下水干旱时间上分布不均匀,在2018年之后发生中度甚至重度的地下水干旱,且SGDI的Theil-Sen变化率为-4.10×10^(-4)/d,未来地下水干旱有显著的增加趋势。③地下水干旱空间上分布不均匀,干旱增加趋势面积占比为63.02%,未来干旱恶化趋势增加,出现自西南向东北加剧现象。④植被变化对地下水干旱的驱动作用不显著。【结论】黄河流域中游地下水干旱较严重,地下水干旱对植被变化存在不显著的响应。

长江中下游流域实际蒸散发演变特征及驱动机制

为了更好地了解长江中下游6个子流域蒸散发量时空演变特征,以及气候和下垫面因子改变对蒸散发量变化的影响,基于GRACE重力卫星观测数据和水量平衡法重建了长江中下游6个子流域实际蒸散发ET序列,评估并融合了3种ET数据集,获得1992—2015年高精度的逐月蒸散发量,分析了6个子流域蒸散发量年值和季节值的变化趋势,引入土地利用程度综合指数La,基于通径分析法定量评估了气候和下垫面因子对各子流域蒸散发量变化的直接和间接影响。结果表明:①3种数据集在长江中下游流域的适用性较好,基于最小二乘权重法的数据融合方法减小了ETrecon与ETNOAH、ETGLEAM的平均差和均方根误差,减小了ETNOAH、ETCR的标准差。②长江中下游流域多年平均蒸散发量为728.7 mm,空间上自西北向东南递增;6个子流域不同季节的蒸散发量均呈升高趋势,其中春、夏季的增幅最大。③各子流域年蒸散发量增加主要由La增强和气温升高所致,气温、La和植被覆盖率等要素的间接作用致使太湖流域风速降低对蒸散发量的影响从正向变为负向。④气温升高促进了NDVI对6个子流域春、夏季蒸散发量增加的正向效应,太湖流域、长江中游和下游干流区秋、冬季降水的增加削弱了辐射降低对蒸散发量变化的作用,而风速上升是洞庭湖流域、中游干流区冬季蒸散发量微弱增加的主导因素。研究结果将为长江中下游流域水资源管理、干旱预测和生态功能评估等研究提供理论基础与科学依据。

“流域-人-歌”三重互联:对长江中下游流域民歌的考察

基于对长江中下游民歌的沿江调查及研究,从“流域-人-歌”三者关系出发,可以发现作为自然区域、作为文化“通道”和“界限”以及作为经济带三种视域下,流域-人-歌三者之间存在互联。随着现代社会经济的发展,传统民歌的存承方式也在发生改变。在国家大力建设长江经济带背景下,应立足于新兴的流域(水域)音乐文化研究,加强对长江流域民歌文化带的保护,进而打造良好的长江经济带文化生态。

黑河流域中游沙荒地元宝枫引种栽培试验研究

元宝枫系一种适应力较强的生态经济型树种。采用客土造林法,在黑河流域中游沙荒地分别栽植陕西杨凌、河南平顶山、山东聊城引进的元宝枫苗木,试验研究表明,1)不同种源的苗木栽植后,栽植成活率最高的是陕西杨凌,为69.3%,分别较山东聊城和河南平顶山高27.2%和32.6%;栽植2年生的元宝枫苗木枝条生长量最大的是陕西杨凌的苗木,枝条平均生长量为108.8cm,分别较山东聊城和河南平顶山枝条平均生长量高16.98%和37.37%;第2年新梢生长量达78.8cm,分别比山东聊城和河南平顶山高34.47%和72.05%;胸径均生长量分别高7.56%和12.04%;2)元宝枫苗木在黑河流域中游沙荒地3月20—25日栽植成活率最高,带土球栽植的较4月20—25日高19.9%,裸根苗高26.3%,胸径生长量均增粗5.81%,新生枝条均生长量提高43.7%;3)带状客土整地后栽植陕西杨凌、河南平顶山和山东聊城的苗木,其成活率分别较局部客土整地提升28.49%、23.61%和25.15%,2年生胸径均生长量增大14.41%、13.57%和14.22%,2年生新生枝条均生长量提高67.9%、43.1%和49.6%。研究成果为元宝枫在黑河流域中游沙荒地引种栽培提供技术支撑。

黑河中游正义峡径流变化趋势及归因分析

以黑河中游正义峡水文站的实测径流量数据为基础,采用线性回归法、Mann-Kendall突变检验法、滑动t检验法、Pettitt检验法和累积距平法分析了正义峡水文站1970―2020年径流序列的变化趋势和突变年份,并利用基于Budyko假设的水热耦合平衡方程,对正义峡径流量变化趋势进行了归因分析。结果表明:(1)研究期内正义峡径流量波动变化,丰枯交替,但整体呈现增加趋势,2004年径流发生突变,突变后的年平均径流量增加了3.08×10^(8)m^(3),增加率为32.7%。(2)突变后的2005―2020年,正义峡径流量对降水、潜在蒸发和下垫面参数的弹性系数分别为1.40、-0.40、-1.57,且各因子对径流的贡献率分别为42.73%、-12.52%、69.79%,表明径流量对下垫面变化最为敏感,气候因子中降水对径流的影响大于潜在蒸发。(3)在一定的区域气候条件下,植被覆盖、土地利用、流域调水等人类活动引起的中游下垫面变化是正义峡径流量变化的主要原因。研究结果可为流域管理部门制定水资源合理分配及调用方案提供科学依据。

三河与中国早期王都

司马迁在《史记·货殖列传》中所称“三河”,是指今天流经山西、河南境内的黄河中下游地区。河东位于今山西南部,襄汾陶寺遗址早期约早出夏代一二百年,或当传说中尧、舜、禹时期,陶寺中晚期已在夏代纪年范围之内,此时正是早期国家形成阶段;河内即今太行山东南麓为古黄河所环绕的地区,历史上为商人的主要活动区域;河南指晋、豫两省黄河以南,周公在此营洛邑,即成周与王城,是周人活动的主要区域。河东、河南、河内三个区域既成相对独立区域,又以黄河相连接,为当时“天下之中”“王者所更居”之地。夏、商、周三代王朝的更替与发展壮大都没有离开过古老的黄河流域,从这个角度看,夏、商、周三代中国早期国家的诞生不仅是黄河与黄河文化的馈赠,同时也把中国历史与中华民族的发展推进到了新的阶段。黄河中下游流域龙山时代形成的文化成果为夏、商、周三代早期国家的诞生奠定了坚实的文化基础,成为夏、商、周三代文明的始原。龙山时代之后不久,在黄河中下游地区诞生了中国历史上最早的国家形态和中华民族的雏形——华夏族。

黄河中游沁河流域环境敏感性分析评价

【研究目的】沁河流域作为黄河流域重要的一级支流,也是黄河流域的重要水土保持功能区,当前面临着水环境遭受破坏以及土壤侵蚀这两个敏感环境问题,环境敏感性评价是用于表征外界干扰对自然生态系统可能造成结果的重要指标,对区域建立生态涵养区的环境政策以及有效进行区域生态建设具有重要作用。【研究方法】根据研究区面临的不同环境地质问题选取了层次分析法(AHP)与RUSLE模型的评价方法以及相关因子,并结合GIS空间数据技术强大的空间分析功能,将图形处理与空间数据运算结合,生成敏感性评价图,评价结果直观,为环境敏感性分析提供了技术支持。【研究结果】针对沁河流域的环境敏感性进行评价,并划分为轻度、中度、高度、极度4类敏感区域,进行统计分析,得出流域内以中、高度敏感区域占比最大,分别占总面积的33.43%、48.56%,同时以各支流流域为依托,针对各类敏感区域的主要环境问题,对其环境现状产生的原因及改善方法提出了相应的调整方案。【结论】依据各区域环境现状及敏感性程度提出了沁河全流域的生态环境保护修复思路,构建一个山地生态系统和平原生态系统有机结合的生态网络格局,致力于改善沁河流域的生态环境现状。

1980-2020年窟野河流域土地利用景观格局演变及其驱动力

[目的]探讨1980—2020年窟野河流域土地利用景观演变过程及其驱动因素,为黄河全流域生态系统的管理与高质量发展提供参考。[方法]选取Landsat系列遥感数据为数据源,利用景观生态学和GIS空间分析对窟野河流域土地利用景观格局变化特征进行分析,并结合气候数据和社会经济数据探讨了窟野河流域土地利用景观格局演变的驱动因素。[结果]窟野河流域耕地面积从1980年的1677.92 km^(2)减少到2020年的1365.58 km^(2);草地面积从1980年的5144.35 km^(2)减少到2020年的5038.97 km^(2);林地面积和建设用地面积分别增加86.07 km^(2),798.96 km^(2),水域面积和未利用土地面积分别减少60.25 km^(2),408.72 km^(2)。1980—2020年窟野河流域土地利用类型转移主要有未利用土地转向耕地和草地,占未利用土地面积减少量的8.63%和61.47%;耕地、草地和未利用土地转向建设用地,占建设用地面积增加量的23.07%,50.98%和10.95%,且2000—2020年土地利用类型转移强度高于1980—2000年。流域内景观斑块表现出斑块数量增加,相连度减小,破碎化程度增加,分割度升高,凝聚度降低和复杂度上升的特征。[结论]气候变化和人类活动都是造成窟野河流域土地利用景观格局演变的影响因素,其中流域内逐年增强的人类活动是促使景观格局发生演变的主要因素,而气候变化是次要因素。

基于模糊综合评判模型的黑河中游水资源承载力评价

评价黑河中游水资源承载力对促进该区域水资源的高效利用并推动经济可持续发展具有重要意义。为此,选取10个主要评价指标,并采用模糊综合评判模型定量分析了黑河中游2000~2020年水资源承载力动态变化状况。结果表明,黑河中游水资源承载力综合评分值在0.3~0.5之间,其中最高值出现在2020年,达到0.471,整体水资源承载力处于中级阶段,即可承载状态。黑河中游应调整用水结构,加强发展节水型经济和生态环境保护,以提高水资源的合理高效利用。

干旱区绿洲-城镇-荒漠景观演变及生态环境效应

绿洲、城镇和荒漠是干旱区内陆河流域重要的景观类型,随着流域社会经济发展,干旱区生态环境问题日益凸显。本研究选取我国西北干旱区第二大内陆河——黑河流域内绿洲-城镇-荒漠的景观组合作为研究对象,利用景观转型核密度与景观结构指数分析2000—2020年期间黑河流域绿洲-城镇-荒漠的时空格局与转型特征,借助多元回归树(MRT)模型探究三类景观转型之间的权衡-协同关系,基于遥感生态指数(RSEI)与景观转型生态贡献率揭示绿洲-城镇-荒漠景观转型的生态环境效应。结果显示:(1)黑河流域荒漠广布,绿洲仅在中下游河道沿岸集中分布,城镇面积占比最小,其空间分布和规模结构与绿洲有紧密关联;(2)黑河流域绿洲-城镇-荒漠景观转型可概括为:农业活动主导期(2000—2005年)、产业快速发展期(2005—2015年)和发展转型协调期(2015—2020年);(3)气温、GDP、海拔、降水量是影响绿洲-城镇-荒漠景观转型之间权衡-协同关系的主要因素;(4)2000—2020年期间流域景观转型以正的生态环境效应为主,耕地扩张是正效应的主导因素;耕地退化、水域减少与草地退化则是带来负效应的主要因素。研究结果可为干旱区内陆河流域实施生态保护与高质量发展提供理论指导。

基于降雨情景模拟的长江中下游流域淹没风险

针对长江中下游流域洪涝灾害频发的现状,基于泰森多边形法和河网密度法分别模拟流域降雨和构建子集水区,采用SCS模型和局部等体积法模拟不同降雨重现期下的淹没水深和范围,并以市为单位进行淹没风险的具体分析。结果表明长江中下游流域产流的高值中心集中在水体和城市用地区域,受淹区主要集中在江汉、两湖平原和长江三角洲等低洼区域;随着降雨重现期的增长,遭遇积水的淹没范围越广,陆域的洪涝程度加剧。降雨量与淹没面积近似呈线性关系,当降雨量<80 mm/d,降雨量每增加1 mm,流域的淹没范围增加947 km^(2);当降雨量>80 mm/d时,淹没范围增加644 km^(2)。在以市为单位的具体分析中,武汉市、南京市、南昌市以及孝感市的淹没范围和风险均较高,因而需重点关注与防御。