Research Progress of the Heihe River Basin Based on Bibliometrics

Water resource is the focus and hinge between ecological environment and socio-economic development. Watershed is the basic unit of hydrology and water resource studies. It is the current hotspot in water science research to carry out the integrated research of the hydrology and water resource at the watershed scale. The Heihe River Basin is the second largest inland river basin in northwestern China, which becomes one of the hot watersheds for its unique hydrological and geographical characteristics. Based on the Web of Science Core Collection, the scientific advances achieved in the Heihe River Basin were estimated from the new sight by combining disciplinary development and problem focus, time evolution and spatial variations. The results indicated that the Heihe River Basin has made positive contribution to the world science in remote sensing, evapotranspiration, water cycle, water resources management and utilization, and climate change research in arid areas. The great achievements has promoted the Heihe River Basin up to the same levels as the international typical basins in the past 30 years, especially after the performances of the major research program entitled “Integrated Study of Eco-hydrological Processes in the Heihe River Basin” (referred to as “Heihe River Program”) supported by a grant from the National Natural Science Foundation of China and large field observation experiments. The number of published articles has ranked the top 20 in the global watershed science research. Some important scientific achievements have been obtained at the mechanisms of eco-hydrological processes in inland river basins, which can actively serve the decision making of the water resource management and sustainable development in the Heihe River Basin. The data mining and contrastive study based on bibliometrics can afford scientific reference for the watershed science research.     

贵州绥阳地质公园白云岩喀斯特景观特征及其形成演化分析

绥阳地质公园,位于贵州高原北部,园区内白云岩喀斯特景观总体可概括为洞穴、高峰丛洼(谷)地、丘陵、峡谷、坡立谷、象形山、天坑、石柱峰、水文遗迹等9大类,它们以中上寒武统娄山关组及下奥陶统桐梓组的白云岩地层为物质基础,有序、集中分布于双河洞、温泉、让水、金钟山等四片以金钟山至让水的分水岭为天然屏障,且相对独立的白云岩区域内,但四片区域相互之间却又以芙蓉江及其支流为连接纽带而紧密相连,共同构成一个以目前亚洲最长洞穴及全球最长白云岩洞穴为核心,峰丛、峡谷、天坑、温泉、地表河、坡立谷等为重要补充,形态优美、珍稀、雄伟、典型,且类型齐全的白云岩喀斯特景观系统。同时在对公园白云岩景观特征及区域地质背景进行分析和研究的基础上,系统研究和探讨了绥阳白云岩喀斯特"一岭两制"式的分异演化过程,并认为它是一个能充分展现白云岩喀斯特复杂演化过程和规律的典型代表地,是全球白云岩喀斯特地貌演化的杰出范例。     

Effects of landuse change on surface runoff and sediment yield at different watershed scales on the Loess Plateau

Erosion and sediment yield from large and small watersheds exhibit different laws. Variations in surface runoff and sediment yield because of landuse change in four watersheds of different scales from 1 km2 to 73 km2 were analyzed. Due to reforestation and farmland terracing, surface runoff and sediment yield reduced by 20-100% and 10-100% respectively. Reductions in surface runoff were differed significantly under different precipitation regimes. For the large watershed (73 km2) landuse change had similar effects on surface runoff regardless of changing of precipitation. For the small watershed (1 km2) landuse change had fewer effects on surface runoff under high precipitation. The relative changes of sediment yield in the four watersheds under reforestation and farmland terracing decreased as precipitation increased from 350 mm to 650 mm, then increased as precipitation increased from 650 mm to 870 mm. Where initial forest coverage rate was below 45%, sediment yield decreased dramatically as forest coverage rate increased. Watershed management with aiming at reducing both surface runoff and sediment yield should be conducted both on sloping surfaces and in channels in large watersheds.     

基于江淮分水岭地区的Z指数修正

利用安徽江淮分水岭地区的合肥、六安、巢湖3个代表站1957—2008年汛期5—9月降水量资料,计算成相应的Z指数,在用Z指数作为旱涝分级指标过程中,发现Z指数理论界限值并不符合江淮分水岭地区的实际情况,因此必须对此进行修改和订正。以微调和旱涝年份数量大体对等为原则进行修正,修正后的7级和5级Z指数界限值较好地反映出江淮分水岭地区实际旱涝,因此修正后的Z指数可以应用到安徽江淮分水岭地区汛期旱涝等级划分中。     

约旦南部瓦迪巴希亚地区铀矿化地球物理特征

通过对瓦迪巴希亚（Wadi Bahiya）地区开展地质调查、岩石取样分析以及地面γ能谱测量等综合研究,认为研究区铀矿化主要产于上白垩统—古新统MCM组近地表风化破碎的灰褐色砂土状泥灰岩之中,矿化类型为现代氧化作用成因的钙结岩型,研究区γ能谱测量铀质量分数平面特征表现为异常规模小,晕圈梯度变化大,深部揭露表明,自近地表向深部铀质量分数逐渐降低,岩石取样分析结果与γ能谱测量具有对应性,铀矿化主要位于地表以下0.5～1.5m的范围内。     

Quickflow response to forest harvesting and recovery in a northern hardwood forest landscape

Forest harvesting often increases catchment quickflow (QF, water delivered rapidly to the stream channel), a metric of high‐flow events controlling a catchment's solute and sediment export. Nevertheless, our understanding of QF responses to various silvicultural strategies (e.g., clearcutting, selection harvest, and shelterwood harvest) is incomplete. We present a 31‐year examination of QF delivery from treatment (clearcut, selection harvest, and shelterwood harvest) and control catchments in a deciduous forest landscape in central Ontario, Canada. Growing season root‐zone storage capacity was estimated using a water balance approach to evaluate temporal changes in QF response to precipitation (P) for pretreatment and posttreatment periods. Threshold relationships between QF and P were assessed for control and treatment catchments for pretreatment and posttreatment periods using piecewise regression. Root‐zone storage capacity demarcated shifts in the hydrologic regime arising from forest harvesting and subsequent regeneration. This was particularly pronounced for clearcutting where postharvest decline in root‐zone storage capacity was followed by a rise to preharvest values. Similar pretreatment threshold relationships between QF and P, and near‐identical P thresholds for producing significant QF, reflected similar soil and overburden depths in the catchments. Harvesting effects were indicated by increases in QF/P ratios for relative small P and the number of P events that generated QF, thus changing treatment QF vs. P threshold relationships. Prior to harvesting there was no significant increase in QF with P below a threshold P of 35–45 mm; however, there was a significant QF vs. P relationship below this threshold for all treatments postharvest. Clearcutting increased the number of QF events for the entire postharvest period and the first 9‐year postharvest compared to the other treatments; nevertheless, evidence for intertreatment differences in total QF depth delivered from the catchments during the growing season was inconclusive. Our work suggests that changes in threshold relationships between QF and P, coupled with knowledge of the physical processes underlying them, are useful when evaluating hydrologic responses to forest harvesting.     

Assessing impacts of riparian buffer zones on sediment and nutrient loadings into streams at watershed scale using an integrated REMM‐SWAT model

Riparian buffer zones in agriculture dominated watersheds play important roles in reducing nonpoint source pollution into aquatic ecosystems and are widely used as a Best Management Practice. Assessment of the effectiveness of riparian buffer zones by modeling method is widely used for watershed management as field measurement‐based assessment is difficult and expensive. The integration of Riparian Ecosystem Management Model (REMM) and Soil and Water Assessment Tool (SWAT) has been developed to simulate the effect of nonpoint source pollution reduction by riparian buffer zones at subbasin scale. However, there are problems in using the integrated model at subbasin scale, as the size of subbasin partition could affect the pollutant reduction rate by riparian buffers. In this study, we partitioned a large watershed with size of 1331 ha into sub‐watersheds with sizes of 666, 333, 166, 83, 51, and 29 ha, and then compared the different simulation results. We found that the modeling could yield more convergent results when the sub‐watersheds were partitioned into suitable size. In the studied area, the suitable sub‐watershed size was less than about 166 ha for runoff and nitrogen and 83 ha for sediment and phosphorus. Among the eight sub‐watersheds (partitioned based on the size of 166 ha), results showed that the effects of riparian buffers on runoff and nutrient loading varied drastically. The reduction rate varied from 0.26% to 30.13% for runoff, 29.4% to 74.07% for sediment, 9.61% to 57.85% for nitrogen, and 18.61% to 68.12% for phosphorus, respectively.     

Combined use of groundwater modeling and potential zone analysis for management of groundwater

A methodology for groundwater evaluation has been developed by the combined use of numerical model and spatial modeling using GIS. The developed methodology has been applied on the sub-basin of the Banganga River, India. Initially, the groundwater potential zones have been delineated by spatial modeling. Different thematic maps of the basin like geology, geomorphology, soil, drainage, slope factor and landuse/landcover have been used to identify the groundwater potential zones. Further, the groundwater flow model for the study area has been developed in the MODFLOW. The groundwater flow vector map has been developed and superimposed on the potential zone map to validate the results of spatial modeling. Finally, the different scenarios have been conceptualized by varying the discharge of the wells and purposing the location for new rainwater harvesting structures. Results reveal that increasing the discharge of the wells in the potential zones put less stress on the aquifer. The suggested locations of rainwater harvesting structures also help to reduce the overall decline of groundwater in the area. The hydrological and spatial modeling presented in this study is highly useful for the evaluation of groundwater resources and for deciding the location of rainwater harvesting structures in semi-arid regions.     

A cost-benefit analysis for the implementation of riparian buffer strips in the Shihmen reservoir watershed

The Shihmen reservoir is an important water source for about 3.4 million people in northern Taiwan. To protect reservoir water quality,it is necessary to conserve and manage the associated watersheds. Riparian buffer strips can trap pollutants emitted near a watershed.The location and design of a buffer strip can influence its pollutant-trapping efficiency.Any commitment of land for use as a riparian buffer strip must consider the project’s economic effectiveness.The present research is a cost-benefit analysis of various possible land developments in the Shihmen reservoir watershed.This study has applied a regression equation to evaluate pollutant-trapping efficiency levels of riparian buffer strips of various widths.Planned buffer strips have been evaluated in terms of net economic effectiveness and benefit-cost ratio.Results indicate that the optimal buffer strip width is 30 m for the Shihmen reservoir watershed.     

Soil Budget,Net Export,and Potential Sinks of Nitrogen in the Lower Oglio River Watershed (Northern Italy)

A nitrogen mass balance, realized for the lower Oglio River basin (Po River Plain, northern Italy), suggested an elevated impact of agricultural activities in this watershed. Livestock manure, synthetic fertilizers, biological fixation, atmospheric deposition, and wastewater sludge contributed 51, 34, 12, 2, and 1% of total N (TN) input, respectively (basin average 450 kg N ha^?1 arable land (AL) year^?1, overall input 100 115 t N year^?1). Crop uptake, ammonia volatilization and denitrification in soils contributed 65, 21, and 14%, respectively, of TN output (basin average 270 kg N ha^?1 AL year^?1, overall output 60 060 t N year^?1). N inputs exceeded outputs by 40 056 t N year^?1, resulting in a basin average surplus of about 180 kg N ha^?1 AL year^?1. About 34% of the N surplus was exported annually from the basin while the remaining amount (about 26 800 t N year^?1) underwent other unaccounted for processes within the watershed. The relevance of nitrogen removal via denitrification in aquatic compartments within the watershed was evaluated. Denitrification in the secondary drainage network can represent a relevant nitrogen sink due to great linear extension (over 12 500 km), with estimated nitrogen loss up to 8500 t N year^?1. Denitrification in the riverbed and in perifluvial wetlands have the potential to remove only a small fraction of the nitrogen surplus (<3%). Evidence suggests the relevance of groundwater as a site of nitrogen accumulation.