Groundwater movement beneath watershed divide is one component of the hydrological cycle that is typically ignored due to difficulty in analysis. Numerical ground-water models, like TAGSAC, have been used extensively ...Groundwater movement beneath watershed divide is one component of the hydrological cycle that is typically ignored due to difficulty in analysis. Numerical ground-water models, like TAGSAC, have been used extensively for predicting aquifer responses to external stresses. In this paper TAGSAC code was developed to identify the inter-basin groundwater transfer (IBGWT) between upper Awash River basin (UARB) and upper rift valley lakes basin (URVLB) of Ethiopia. For the identification three steady state groundwater models (for UARB, URVLB and for the two combined basins) were first created and calibrated for the 926 inventoried wells. The first two models are conceptualized by considering the watershed divide between the two basins as no-flow. The third model avoids the surface water divide which justifies IBGWT. The calibration of these three models was made by changing the recharge and hydrogeologic parameters of the basins. The goodness of fit indicators (GoFIs) obtained was better for the combined model than the model that describes the URVLB. Furthermore, the hydraulic head distribution obtained from the combined model clearly indicates that there is a groundwater flow that doesn’t respect the surface water divide. The most obvious effect of IBGWT observed in these two basins is that it diminishes surface water discharge from URVLB, and enhances discharge in the UARB. Moreover, the result of this study indicates potential for internal and cross contamination of the two adjacent groundwater.展开更多
Siliceous stomatocysts of chrysophyte algae, along with diatom frustules, are well preserved in bottom sediments of various water bodies. Analysis of microfossils from a core sample of the Upper Pleistocene and Holoce...Siliceous stomatocysts of chrysophyte algae, along with diatom frustules, are well preserved in bottom sediments of various water bodies. Analysis of microfossils from a core sample of the Upper Pleistocene and Holocene sediments from the southern part of Lake Hovsgol revealed 36 different morphotypes of chrysophycean stomatocysts. Some of them were attributed to species of the genera Mallomonas Perty, Chrysosphaerella Lauterborn., Paraphysomonas (Stokes) De Saedeleer, and Dinobryon Ehr.;20 morphotypes were described as novel. The abundance and diversity of stomatocyst morphotypes in the core sample varied depending on the age of sediments. The results obtained in the study broaden views on the biological diversity of microalgae and confirm that chrysophycean stomatocysts can serve as good environmental indicators in paleolimnological and paleoclimatic reconstructions.展开更多
Demand for fresh water, as one of the major natural resources, is increasing rapidly with increasing development and environmental degradation. The continued abstraction of water from Lake Ziway and its main feeder ri...Demand for fresh water, as one of the major natural resources, is increasing rapidly with increasing development and environmental degradation. The continued abstraction of water from Lake Ziway and its main feeder rivers Meki and Katar for irrigation indicates that the water demand may soon exceed the supply. To illustrate disparities in spatial distribution of water resources, the Upper Awash sub-basin, which shares a water-divide with the CRVL sub-basin, has large flow volumes particularly in the rainy season and suffers with seasonal flooding. The rationale behind regaining the water in CRVL relies on this non-uniform spatial distribution of fresh water, calling for a balance between water surplus and deficit regions. For this reason, Inter Basin Water Transfer (IBWT) is suggested as a viable option to augment utilizable water resources of the Upper Awash sub-basin to reduce the significant pressure on the water supply of the rapidly developing urban and irrigation areas in the CRVL sub-basin. A water evaluation and planning (WEAP) model was used to quantify the amount of surplus water in the donor basin, when examining the hydrological dynamics of the basins. Furthermore, optimal flow diversion scenarios were generated by maintaining two baseline scenario constraints. The estimated surplus water in the rainy season is expected to contribute 18 million cubic meters (mcm), 88 mcm and 192 mcm in months June, July and August respectively under average conditions. The optimal amount of diverted water could potentially stabilize the environmental degradation of Lake Ziway and Lake Abijata by compensating for development-driven abstraction and surface water evaporation respectively.展开更多
The Upper Triassic Xujiahe （须家河） Formation in the Sichuan （四川） Basin, Southwest China is distinctive for the basin-scale sand deposition. This relatively rare sedimentary phenomenon has not been well interpre...The Upper Triassic Xujiahe （须家河） Formation in the Sichuan （四川） Basin, Southwest China is distinctive for the basin-scale sand deposition. This relatively rare sedimentary phenomenon has not been well interpreted. Here we addressed this issue by discussing sedimentary framework and conceptual model. Analysis of sedimentary setting implied that the basin received transgression during the deposition. It had multiple provenance supplies and river networks, as being surrounded by old- lands in multiple directions including the north, east and south. Thus, the basin was generally charac-terized by coastal and widely open and shallow lacustrine deposition during the Late Triassic Xujiahe period. This is similar to the modern well-known Poyang （鄱阳） Lake. Therefore, we investigated the framework and conceptual model of the Sichuan Basin during the Xujiahe period with an analogue to the Poyang Lake. Results show that the conceptual model of the deposition can be divided into transgressive and regressive stages. The first, third and fifth mem- bers of the formation are in transgressive stage and the deposits are dominated by shore and shallow lacustrine mud. In contrast, the deposition is mainly of braided river channel sand deposits during the regressive stage, mainly including the second, fourth and sixth members of the formation. The sand deposited in almost the entire basin because of the lateral migration and forward moving of the cross networks of the braided rivers. The multiple alternations of short and rapid transgression and relatively long regression are beneficial to the basin-scale sand deposition. Thus, the main channel of the braided river and its extensional areas are favorable for the development of hydrocarbon reservoir. This provides practical significance to the reservoir evaluation and exploration. In addition, the results also justify the relatively distinctive sedimentary phenomenon in the study area and may also have im- plications for understanding the large-scale sand deposition elsewhere.展开更多
功能区划作为自然保护区进行科学布局和功能定位的重要手段,旨在促进生态系统服务功能的协同发挥。运用Marxan with Zones模型方法,将生态系统服务权衡分析纳入到安徽升金湖国家级自然保护区的功能区划研究,并展开情景模拟,得出不同生...功能区划作为自然保护区进行科学布局和功能定位的重要手段,旨在促进生态系统服务功能的协同发挥。运用Marxan with Zones模型方法,将生态系统服务权衡分析纳入到安徽升金湖国家级自然保护区的功能区划研究,并展开情景模拟,得出不同生态系统服务保护目标下的功能区划方案。结论如下:(1)保护区的上湖区域及其周边河流入湖区域的生物多样性和防洪蓄水价值较高;东南部林地区域的水源涵养与碳储存价值较高,食物生产价值从西北部到东南部逐渐降低;社会文化价值较高的区域主要是沿湖地带。(2)生态系统服务之间存在不同程度的权衡/协同关系,其中,生物多样性作为关键生态系统服务,与其它生态系统服务之间存在显著的权衡/协同关系,根据相关性系数大小可分为高协同关系(防洪蓄水)、低协同关系(水源涵养和社会文化)与权衡关系(碳储存和食物生产)。(3)生态系统服务权衡关系视角下的不同保护目标分配得到的功能区划情景均表现出核心区面积大幅增加的特征。此外,高协同情景下的功能区划更能兼顾多种生态系统服务,且对不同典型珍稀濒危鸟类的保护强度更大,能够总体上改善生态系统服务之间的权衡关系,提升生物多样性与防洪蓄水和水源涵养的协同关系,并降低与碳储存的权衡关系。展开更多
文摘Groundwater movement beneath watershed divide is one component of the hydrological cycle that is typically ignored due to difficulty in analysis. Numerical ground-water models, like TAGSAC, have been used extensively for predicting aquifer responses to external stresses. In this paper TAGSAC code was developed to identify the inter-basin groundwater transfer (IBGWT) between upper Awash River basin (UARB) and upper rift valley lakes basin (URVLB) of Ethiopia. For the identification three steady state groundwater models (for UARB, URVLB and for the two combined basins) were first created and calibrated for the 926 inventoried wells. The first two models are conceptualized by considering the watershed divide between the two basins as no-flow. The third model avoids the surface water divide which justifies IBGWT. The calibration of these three models was made by changing the recharge and hydrogeologic parameters of the basins. The goodness of fit indicators (GoFIs) obtained was better for the combined model than the model that describes the URVLB. Furthermore, the hydraulic head distribution obtained from the combined model clearly indicates that there is a groundwater flow that doesn’t respect the surface water divide. The most obvious effect of IBGWT observed in these two basins is that it diminishes surface water discharge from URVLB, and enhances discharge in the UARB. Moreover, the result of this study indicates potential for internal and cross contamination of the two adjacent groundwater.
文摘Siliceous stomatocysts of chrysophyte algae, along with diatom frustules, are well preserved in bottom sediments of various water bodies. Analysis of microfossils from a core sample of the Upper Pleistocene and Holocene sediments from the southern part of Lake Hovsgol revealed 36 different morphotypes of chrysophycean stomatocysts. Some of them were attributed to species of the genera Mallomonas Perty, Chrysosphaerella Lauterborn., Paraphysomonas (Stokes) De Saedeleer, and Dinobryon Ehr.;20 morphotypes were described as novel. The abundance and diversity of stomatocyst morphotypes in the core sample varied depending on the age of sediments. The results obtained in the study broaden views on the biological diversity of microalgae and confirm that chrysophycean stomatocysts can serve as good environmental indicators in paleolimnological and paleoclimatic reconstructions.
文摘Demand for fresh water, as one of the major natural resources, is increasing rapidly with increasing development and environmental degradation. The continued abstraction of water from Lake Ziway and its main feeder rivers Meki and Katar for irrigation indicates that the water demand may soon exceed the supply. To illustrate disparities in spatial distribution of water resources, the Upper Awash sub-basin, which shares a water-divide with the CRVL sub-basin, has large flow volumes particularly in the rainy season and suffers with seasonal flooding. The rationale behind regaining the water in CRVL relies on this non-uniform spatial distribution of fresh water, calling for a balance between water surplus and deficit regions. For this reason, Inter Basin Water Transfer (IBWT) is suggested as a viable option to augment utilizable water resources of the Upper Awash sub-basin to reduce the significant pressure on the water supply of the rapidly developing urban and irrigation areas in the CRVL sub-basin. A water evaluation and planning (WEAP) model was used to quantify the amount of surplus water in the donor basin, when examining the hydrological dynamics of the basins. Furthermore, optimal flow diversion scenarios were generated by maintaining two baseline scenario constraints. The estimated surplus water in the rainy season is expected to contribute 18 million cubic meters (mcm), 88 mcm and 192 mcm in months June, July and August respectively under average conditions. The optimal amount of diverted water could potentially stabilize the environmental degradation of Lake Ziway and Lake Abijata by compensating for development-driven abstraction and surface water evaporation respectively.
基金supported by the Major State Basic Research Development Program(No.2012CB 214803)the China's National Science & Technology Special Project (No.2011ZX05004-005-03)+1 种基金the PetroChina Youth Innovation Foundation(No.2011D-5006-0105)the Key Subject Construction Project of Sichuan Province,China(No.SZD0414)
文摘The Upper Triassic Xujiahe （须家河） Formation in the Sichuan （四川） Basin, Southwest China is distinctive for the basin-scale sand deposition. This relatively rare sedimentary phenomenon has not been well interpreted. Here we addressed this issue by discussing sedimentary framework and conceptual model. Analysis of sedimentary setting implied that the basin received transgression during the deposition. It had multiple provenance supplies and river networks, as being surrounded by old- lands in multiple directions including the north, east and south. Thus, the basin was generally charac-terized by coastal and widely open and shallow lacustrine deposition during the Late Triassic Xujiahe period. This is similar to the modern well-known Poyang （鄱阳） Lake. Therefore, we investigated the framework and conceptual model of the Sichuan Basin during the Xujiahe period with an analogue to the Poyang Lake. Results show that the conceptual model of the deposition can be divided into transgressive and regressive stages. The first, third and fifth mem- bers of the formation are in transgressive stage and the deposits are dominated by shore and shallow lacustrine mud. In contrast, the deposition is mainly of braided river channel sand deposits during the regressive stage, mainly including the second, fourth and sixth members of the formation. The sand deposited in almost the entire basin because of the lateral migration and forward moving of the cross networks of the braided rivers. The multiple alternations of short and rapid transgression and relatively long regression are beneficial to the basin-scale sand deposition. Thus, the main channel of the braided river and its extensional areas are favorable for the development of hydrocarbon reservoir. This provides practical significance to the reservoir evaluation and exploration. In addition, the results also justify the relatively distinctive sedimentary phenomenon in the study area and may also have im- plications for understanding the large-scale sand deposition elsewhere.
文摘功能区划作为自然保护区进行科学布局和功能定位的重要手段,旨在促进生态系统服务功能的协同发挥。运用Marxan with Zones模型方法,将生态系统服务权衡分析纳入到安徽升金湖国家级自然保护区的功能区划研究,并展开情景模拟,得出不同生态系统服务保护目标下的功能区划方案。结论如下:(1)保护区的上湖区域及其周边河流入湖区域的生物多样性和防洪蓄水价值较高;东南部林地区域的水源涵养与碳储存价值较高,食物生产价值从西北部到东南部逐渐降低;社会文化价值较高的区域主要是沿湖地带。(2)生态系统服务之间存在不同程度的权衡/协同关系,其中,生物多样性作为关键生态系统服务,与其它生态系统服务之间存在显著的权衡/协同关系,根据相关性系数大小可分为高协同关系(防洪蓄水)、低协同关系(水源涵养和社会文化)与权衡关系(碳储存和食物生产)。(3)生态系统服务权衡关系视角下的不同保护目标分配得到的功能区划情景均表现出核心区面积大幅增加的特征。此外,高协同情景下的功能区划更能兼顾多种生态系统服务,且对不同典型珍稀濒危鸟类的保护强度更大,能够总体上改善生态系统服务之间的权衡关系,提升生物多样性与防洪蓄水和水源涵养的协同关系,并降低与碳储存的权衡关系。
基金Supported partly by the National Natural Science Foundation of China(30870317)EU-China Biodiversity Programme(00056783)Anhui Academic and Technical Leader Fund
