Performance evaluation of lake basin water governance using composite index

A Lake Basin Water Governance Performance Composite Index (LBWGPCI) framework was developed to test and evaluate the performance of water governance for lake basins using the Songkhla Lake Basin (SLB), Thailand as a case study. The LBWGPCI integrates a range of water resources and environmental related indicators together to provide a holistic profile of lake basin key water governance issues. The purpose of this work was to identify, examine, develop and analyze key lake basin water governance performance indicators, test them on the SLB, and make appropriate recommendations for improvement. In the light of the results obtained in this study, overall composite index of the LBWGPCI indicated poor performance, which required high priority, urgent and critical actions. We conclude that the water governance performance of the SLB is still evolving and has a lot of great potential to grow in the right direction if the current focus and commitment of government and stakeholders at all levels, are maintained and sustained.     

东江湖流域水供给服务时空格局分析

与水相关的生态系统服务是生态学研究的热点问题。水供给服务对区域水循环和水量平衡具有至关重要的作用。东江湖流域是国家重点流域和水资源生态补偿试点,水供给服务是该流域生态系统服务保护的重中之重。基于In VEST模型,从流域、子流域两个尺度分析1995—2010年东江湖流域的水供给服务时空格局,并比较了不同土地覆被类型的水供给服务能力。结果表明:(1)1995—2010年,东江湖流域水供给量整体呈现先增加后减少的趋势,年均水供给量在1100—1600 mm之间,2000年的平均水供给量最多。(2)各年水供给量的空间分布格局相似,由湖区向四周递增。(3)平均水供给量较高的土地覆被类型为城镇建设用地、典型草地、灌丛、灌丛草地,在1600 mm左右。平均水供给量较低的土地覆被类型为河湖滩地、内陆水体、水田,在800 mm以下。(4)各个子流域平均水供给量大致在750—1700 mm之间。东北部子流域为水供给服务的高值地区。从水量平衡的角度而言,降水和实际蒸散发是决定生态系统水供给量的两个关键环节。东江湖流域水供给量的时空格局差异是气候和土地覆被共同作用的结果。研究能够为东江湖流域的水资源管理提供科学的参考依据,对东江湖流域生态系统服务功能的提升、生态环境质量的改善、社会经济的可持续发展具有重要的现实意义。     

基于GIS的鄱阳湖流域生态系统服务价值结构变化研究

鄱阳湖作为中国最大的淡水湖,国际重要湿地,其生态环境保护与可持续发展意义重大。基于生态系统服务价值分析方法,以鄱阳湖全流域为研究区,利用1990年、2000年、2008年3个时期数据,分别从全流域与子区域两个层次,计算了生态系统服务价值。并且基于威弗(Weaver)组合指数,求出了鄱阳湖各子流域的生态系统服务价值结构与坡度结构类型。分析表明,鄱阳湖流域在3个时期生态系统服务价值量持续增大,全流域的可持续性向有利的方向发展。在各子区域中,大部分区域生态系统服务价值较高,可持续发展水平较好,且呈现良性发展趋势,但是在鄱阳湖流域的中部地区生态系统服务价值较低,可持续发展水平较差,且呈现不良发展趋势。鄱阳湖流域的生态系统服务价值组合结构以林地、农用地、水体3类为主,且单重结构类型所占比例最大,双重结构类型与三重结构类型次之;坡度类型以小于15°的组合类型为主,结构类型除三重结构类型外,其它类型分布均较多。促进流域可持续发展向更高水平发展,在全流域角度,应该继续执行退耕还林、还湖工程,严格控制建设用地的增加;从子区域的角度,对鄱阳湖流域的中部地区应该控制建设用地与农用地对林地、草地的占用,严格执行退耕还林、还草工程。从生态系统服务价值结构角度,对于山地丘陵区,应该加大对生态环境的维护,并且合理的发展林业经济以促进经济发展;对于环鄱阳湖平原区,应该推进资源消耗少,污染排放小,高科技产业,促进湖区生态环境保护与社会经济的协调发展。     

巢湖流域生态安全评价研究

目前,巢湖流域的生态安全问题非常突出,已严重影响流域社会经济的可持续发展。基于巢湖流域社会经济、水体环境质量及水生生态系统的数据资料,应用驱动力-压力-状态-影响-响应(DPSIR)模型,提出了基于水环境和水生态的巢湖流域生态安全评价框架模型和指标体系,并采用熵权物元模糊评价法进行巢湖流域生态安全评价研究。研究结果表明,2003和2007年巢湖流域整体处于生态安全中度风险状态,水体环境质量的变化和水生生态系统的演替将严重威胁巢湖流域的生态安全,水体中的TP浓度、NH-N浓度以及TN浓度是决定巢湖流域生态安全的最关键因子。     

南四湖流域关键生态系统服务的时空权衡关系

从多尺度科学地研究流域各生态系统服务间的权衡与协同关系,对流域实现经济发展与生态保护双重目标具有重要研究意义。运用InVEST模型模拟评估产水量、水质净化、土壤保持、碳存储、生物多样性维持和授粉等6类区域关键生态系统服务,并通过热点分析、相关分析和主成分分析,定量分析自改革开放以来（1980-2018年）这些生态系统服务的时空变化及其在不同尺度上的权衡关系。结果表明：（1）南四湖流域产水服务呈上升趋势,而水质净化、土壤保持、碳储存、生境质量、授粉等服务则总体呈下降趋势。（2）研究区东部林地和草地广布,是碳存储、生境质量和授粉服务的高值区,而建设用地分布的地区是产水量和土壤保持服务的高值区。（3）产水量与水质净化服务之间呈权衡关系,水质净化与生境质量、碳存储与授粉之间则存在较强的协同关系。（4）在子流域尺度上主要是存在着供给服务（产水量）与调节服务（水质净化和土壤保持）、供给服务（产水量）与支持服务（生境质量）之间的空间权衡关系;在县域尺度上,供给服务、调节服务与支持服务（产水量、水质净化、碳存储、生境质量和授粉）之间主要是空间协同关系,两个尺度之间具有较大差异。研究结果可为管理者在合适的空间尺度上制定相应的政策提供科学支撑,促进南四湖流域生态环境和社会经济协同发展。     

基于风险-质量的高原湖泊流域生态分区构建——以滇池流域为例

随着人类足迹不断延伸,高原湖泊流域人地系统三生空间冲突显著。以滇池流域为例,顾及流域三生空间冲突风险,基于三生空间景观格局和生态环境质量的变化,尝试引入四象限模型,结合热点分析,划分风险-质量综合生态环境分区。结果表明:(1)滇池流域三生空间冲突风险类型以较强为主,冲突曲线指数呈现倒"U"型,较强冲突比重不断下降。三生空间类型转换明显,生活空间共增长了312.23km²,主要是由于高原湖泊流域的快速城镇化使得生活空间大量挤占了生产和生态空间。(2)滇池流域生态环境质量总体呈现下降趋势,空间上以滇池为中心呈现高-低-高的分布特征。较高质量和高质量区面积减少了136.66km²;低质量区和较低质量区由699.65km²上升到930.51km²,约占流域总面积的1/3。(3)基于三生空间冲突风险和生态环境质量两个维度将生态分区分为综合生态环境优质、良好、一般、劣质四类,四类区的空间分布连续性相对较好,尤以劣质区面积连续扩展的态势最为典型。针对不同生态分区提出差异化管理措施,为流域人地协调发展提供实践指导。     

基于生态系统服务的青海湖流域生态风险评估及其空间异质性影响因素分析

青海湖流域是我国西北部的"气候调节器"和"空气加湿器",其生态风险管控对青藏高原乃至我国西部的生态保护和可持续发展都有着重要意义。基于InVEST模型对青海湖流域2005年、2010年、2015年、2020年产水量、土壤保持、生境质量和碳储存4项生态系统服务进行定量评估,借助熵权-TOPSIS法,以生态系统服务的相对损失量来构建区域生态风险指数,并运用地理探测器和地理加权回归模型分析自然-社会要素对青海湖流域生态风险空间异质性的影响。结果表明:(1)2005-2020年青海湖流域产水量、土壤保持、生境质量和碳储存均呈现波动增加的趋势,增幅分别为10.17%、18.36%、9.84%、3.47%,各项生态系统服务的高值区分布于河流上游的河源区和植被覆盖率高的林地区域;(2)2005-2020年青海湖流域生态风险较高,但呈现波动降低的趋势。高风险区主要位于湖区、环湖区、布哈河河谷以及流域西北部;(3)青海湖流域生态风险的空间格局受地形及高程因子主导,但人为干扰度的影响力呈逐年上升趋势。驱动因子交互作用的解释力显著高于单因子;(4)主要驱动因子对研究区生态风险的作用方向及强度存在明显的空间分异特征,坡度呈正相关,年平均气温呈负相关,归一化植被指数(NDVI)和人为干扰度呈现出正负两种效应,但以正向效应为主。研究结果对青海湖流域生态风险管控和高原生态环境保护有一定借鉴意义。     

Geographical ancestry of Lake Malawi's cichlid fish diversity

The Lake Malawi haplochromine cichlid flock is one of the largest vertebrate adaptive radiations. The geographical source of the radiation has been assumed to be rivers to the south and east of Lake Malawi, where extant representatives of the flock are now present. Here, we provide mitochondrial DNA evidence suggesting the sister taxon to the Lake Malawi radiation is within the Great Ruaha river in Tanzania, north of Lake Malawi. Estimates of the time of divergence between the Lake Malawi flock and this riverine sister taxon range from 2.13 to 6.76 Ma, prior to origins of the current radiation 1.20–4.06 Ma. These results are congruent with evaluations of 2–3.75 Ma fossil material that suggest past faunal connections between Lake Malawi and the Ruaha. We propose that ancestors of the Malawi radiation became isolated within the catchment during Pliocene rifting that formed both Lake Malawi and the Kipengere/Livingstone mountain range, before colonizing rivers to the south and east of the lake region and radiating within the lake basin. Identification of this sister taxon allows tests of whether standing genetic diversity has predisposed Lake Malawi cichlids to rapid speciation and adaptive radiation.     

Ecosystem evolution of Lake Gusinoe (Transbaikal region, Russia)

Lake Gusinoe is situated on a basin originating from Paleozoic and Mesozoic deposits. The recorded history of the lake's ecosystem evolution is no more than 300 years. The present lake drainage basin was formed mainly in the Cenozoic era, but during the past century, major anthropogenic impacts on the lake have occurred. The human-influenced evolution of the ecosystem began in the 1940s with the development of opencut coal mining nearby the lake. Population increase and the building of the Gusinoozersk State Regional Power Plant, the Trans-Mongolian Railroad and an associated station, and military installations were the major sources of anthropogenic impacts. Since the early 1950s about five species of fish have been introduced into Lake Gusinoe or have invaded the lake, and at least six of the native species have disappeared or are in danger of extinction. From our recent investigations, the present environment of the Lake Gusinoe Basin (Gusinoozersk Basin) is divided into four zones hydrogeochemically: (1) ultrafreshwater, (2) freshwater, (3) mineralized water, and (4) hyposaline and saltwater. Some additional data on changes of the chemical components of the drainage basin waters, as well as on the transition of zooplankton and zoobenthic fauna, are presented in consideration of the risk of industrial development, and the perspectives are discussed.     

近40年来洞庭湖流域土地利用及生态风险时空演变分析

以洞庭湖流域为研究对象,利用1980年、1990年、2000年、2010年和2018年5个时期的土地利用数据,在定量分析近40年流域土地利用动态特征的基础上,从景观生态学视角构建生态风险评价模型,对1980-2018年洞庭湖流域生态风险进行评价,并进一步揭示其时空格局演变特征。结果表明：（1）1980年以来,洞庭湖流域土地利用类型以林地和耕地为主。洞庭湖流域土地利用格局发生较大变化,其显著特征为建设用地不断扩张、林地基本稳定、耕地日益萎缩和水域呈扩大趋势。（2）近40年来,洞庭湖流域生态环境较为良好,以较低和中等生态风险区为主导类型。在1980-1990年、1990-2010年和2010-2018年3个时段内,生态风险呈现增长、缓和、加剧的变化过程,高风险区以洞庭湖湖盆向环洞庭湖平原扩张,洞庭湖区、湘江流域和资水流域生态风险等级明显高于其他地区,而沅水流域、澧水流域和湘江流域的东南部生态风险相对较小。     

基于全球气候模式集合的鄱阳湖流域未来潜在蒸散量及其干旱效应研究

鄱阳湖流域近年来旱涝灾害频发,原有的水量平衡被打破。因此,开展鄱阳湖地区潜在蒸散量及干旱效应研究具有重要意义。潜在蒸散量（Reference Evapotranspiration,ET₀）是评价区域水资源配置和计算干旱指数的重要指标。以我国的鄱阳湖流域为研究区,依托统计降尺度模型,基于站点观测数据、气候模式数据以及美国环境中心再分析数据,运用遗传算法构建多模式集合,模拟未来情景下流域潜在蒸散量和干旱指数（Drought Index,DI）时空演变特征。结果表明：基于遗传算法构建的模式集合较单一气候模式或等权模式集合,模拟性能佳;RCP4.5、8.5情景下流域ET₀均呈上升趋势,ET₀变化的第一主周期分别为20年和4年,流域ET₀未来空间变化特征表现为东高西低;RCP8.5情景下,鄱阳湖流域DI在年际上呈显著上升趋势,9-11月是干旱风险防范的关键时期;流域年DI变化的主周期为8年,流域的中东部地区将是未来干旱风险防范的重点区域。本研究为认识区域尺度下气候变化对潜在蒸散量的影响提供借鉴,同时为政府部门科学应对鄱阳湖流域未来时期可能出现的旱情提供的决策支持。     

面向湖泊生态系统健康维护的生态管控分区研究——以红枫湖流域为例

以湖泊生态系统健康维护为目标的生态管控分区成为水环境保护与治理的重要手段,有助于全面掌握流域生态状况,对流域生态经济可持续发展具有重要参考价值。以红枫湖流域为例,从水文水资源、物理结构、水质、生物、社会服务功能5个方面对湖泊生态系统健康进行评价。运用ArcGIS空间分析工具,以200 m×200 m格网为评价单元辨析流域生态敏感性和生态服务功能空间分异特征,进而运用SOFM聚类方法优选聚类方案,划定生态管控分区。结果表明：1）红枫湖湖泊生态系统健康评分为68.4分,属健康状态,物理结构是当前威胁红枫湖湖泊生态系统健康的主要因子;2）红枫湖流域生态敏感性及生态服务功能空间差异明显,生态环境脆弱,生态服务功能较低;3）红枫湖流域生态管控分区划为优先控制区、重点控制区、缓冲控制区及一般控制区,应实施差异化管理,重点任务是调结构、转方式,逐步修复生态系统。     

Oxygen concentration profiles in sediments of two ancient lakes: Lake Baikal (Siberia,Russia) and Lake Malawi (East Africa)

Oxygen concentration profiles have been measured, by means of with microelectrodes in sediments of Lake Baikal and Lake Malawi, along transects allowing to give a survey of two major ancient Rift lakes: Lake Baikal (Eastern Siberia) and Lake Malawi (East Africa), along depth transects in the constitutive basins of the lakes and/or of relevant depths with regard to oxygen (including including the deepest point, 1680 m, in Lake Baikal). Sediment oxygen penetration depths (SOPs) display very different patterns, depending on the lake in the two lakes. In Lake Baikal, SOPs are variable, show no significant relationship with bathymetric depth and are surprisingly deep on Akademichesky ridge (> 50.0 mm), emphasizing the distinctive feature of this region in the lake. While the Selenga river is an important source of eutrophication, the similarity of SOP-values in the Selenga shallow with those of most other sites suggests either a dilution of organic material by allochthonous matter, or a strong south-to-north transport of particles. In Lake Malawi, available oxygen is restricted to a maximum of three millimetres of the sediment, and there is a negative relationship with bathymetric depth, as a result of a steady decline of oxygen concentration with depth through the water column. Amongst the few parameters known to affect SOPs, the oxygen consumption by the sediment seems the most significant in both lakes. SOP-values furthermore confirm differences in the trophic status of Baikal and Malawi, respectively. The importance of oxygen as a factor likely to create ecological segregation for benthic organisms is discussed. Lake Malawi offers possibilities of bathymetric segregation but no vertical segregation in the sediment. In contrast, no bathymetric segregation related to oxygen is possible in Lake Baikal, but vertical segregation in the sediment is very likely. This revised version was published online in July 2006 with corrections to the Cover Date.     

Biodiversity pattern of fish assemblages in Poyang Lake Basin: Threat and conservation

Poyang Lake Basin is of great importance to maintain regional ecological balance. However, fish biodiversity in this basin has rapidly declined as the result of anthropogenic habitat alteration, such as dam construction, sand mining, and water pollution. Here, we aimed to analyze the temporal and spatial changes in biodiversity patterns of fish in Poyang Lake Basin over the last 37 years. The number of fish species underwent a significant decrease in the current period. In particular, 36.7% of the migration of fish was extirpated. Twenty‐seven fish species have been formally assessed using the Chinese Red List were currently listed as Critically Endangered (9), Endangered (3), Vulnerable (10), and Near Threatened (5). Alpha and gamma diversity revealed that fish diversity had also decreased, and beta diversity showed significant composition dissimilarity in two periods. PCoA showed that the historical fish composition dissimilarity was significantly different from that of the current period. We found a significant effect of the geographical distance on the spatial turnover component for the historical and current periods. In addition, the nestedness component was the main contributor to beta diversity, which indicated one large protected area should be established in Poyang Lake and the Ganjiang River Basin with higher species richness. These results indicated that fish biodiversity declined in the current period likely caused by anthropogenic habitat alteration and other threatened factors. Therefore, we suggest that the habitat reconstruction and biodiversity conservation for fish have become imperative in this basin, and a complete management plan should be carried out.     

Understanding future ecosystem changes in Lake Victoria basin using participatory local scenarios

Understanding future ecosystem changes is central to sustainable natural resource management especially when coupled with in-depth understanding of impacts of drivers, such as governance, demographic, economic and climate variations and land use policy. This offers comprehensive information for sustainable ecosystem services provision. A foresight process of systematic and presumptive assessment of future state and ecosystem integrity of Lake Victoria basin, as participatory scenario building technique, is presented. Four scenarios have been illustrated as possible future states of the basin over the next twenty years. Using a scenario building model developed in Ventana Simulation (VENSIM^®) platform, the paper presents a scenario methodology for tracking changes in lake basin ecosystem status. Plausible trends in land use change, changes in lake levels and contribution of fisheries are presented. This is part of an initial attempt to setup long-term environmental policy planning strategies for Lake Victoria basin. The assumptions, driving forces, impacts and opportunities under each scenario depict major departure and convergence points for an integrated transboundary diagnosis and analysis of regional issues in the basin as well as strategic action planning for long-term interventions. The findings have been presented in terms of temporal, spatial, biophysical and human well-being dimensions. The attempts in this study can be embedded in a policy framework for basin management priority setting and may guide partnerships for environmental management.     

Migratory behaviour shapes spatial genetic structure of cyprinid fishes within the Lake Malawi catchment

• Genetic differences among freshwater fish populations are dependent on life‐history characteristics of the species, including the range of adult dispersal and the extent of homing to natal breeding grounds. However, the effects of variation in such characteristics on population genetic connectivity are rarely studied comparatively among closely related species.
• We studied population genetic structure within three congeneric cyprinid species from the Lake Malawi catchment that differ substantially in life‐history traits and conservation status, using a combination of microsatellite and mitochondrial DNA markers. Mpasa (Opsaridium microlepis) is a large (70 cm total length) migratory species that spawns in rivers, but as an adult is exclusively known from the main lake body. Sanjika (Opsaridium microcephalum), is a medium size (30 cm total length) species that exists in lake breeding, river‐lake migratory and apparently landlocked populations. Dwarf sanjika (Opsaridium tweddleorum) is a small non‐migratory species (15 cm total length) that persists in small tributaries surrounding the main lake and adjoining rivers.
• The results revealed striking differences among the three species in spatial genetic structuring. The river‐lake migratory mpasa showed only weak yet significant population genetic structure within the main Lake Malawi catchment, suggesting that there is no strong natal homing. The habitat‐generalist sanjika showed only weak spatial genetic differentiation at microsatellite loci within the Lake Malawi catchment, but moderate structure in mitochondrial DNA, potentially reflecting male‐biased dispersal. The river‐restricted dwarf sanjika showed strong genetic structure in both microsatellite and mitochondrial DNA, suggesting strictly limited dispersal at both adult and juvenile stages.
• We conclude that contrasting migration life histories have resulted in dramatically different patterns of population genetic structure among these congeneric species. The observed patterns demonstrate how divergent life‐history evolution may strongly influence broader patterns of population genetic connectivity in freshwater fish, with consequences for management and conservation. Specifically the results suggesting gene flow among Lake Malawi populations of mpasa, an IUCN red‐listed ‘Endangered’ species endemic to the lake catchment, imply that conservation initiatives operating at both local and catchment scales are needed to reverse local population decline.

     

Genetic homogeneity among breeding grounds and nursery areas of an exploited Lake Malawi cichlid fish

1. Nursery areas are commonly recognized as important habitats for the management and conservation of fish stocks. Here we report the use of nursery areas by an exploited offshore cichlid in Lake Malawi, Rhamphochromis longiceps .
2. Like all haplochromine cichlids that have been studied, the species is a maternal mouthbrooder that broods eggs for several weeks following spawning. We found evidence that during this brooding period females migrate from open water to release juveniles in three shallow peripheral waterbodies (Chia Lagoon, Unaka Lagoon, Lake Malombe). However, it was unclear whether there is geographical population structuring within the species, which could indicate stock differences in their use of these nursery habitats, or if the lake contains a genetically panmictic population that employs nursery habitats opportunistically.
3. To investigate spatial and temporal population structuring within the lake we genotyped populations at seven microsatellite DNA loci. Overall, we found no significant spatial structuring among juveniles from the peripheral lagoons or among breeding males within the main lake body. Moreover, we found no evidence of temporal structuring among males on the breeding grounds within Lake Malawi or females entering Chia lagoon. Together, these results suggest that Lake Malawi contains a genetically homogeneous population of R. longiceps .
4. At present we know little of the distribution of juvenile R. longiceps elsewhere in the Lake Malawi basin, but their absence from surveyed rocky and sandy littoral habitats makes it possible that the species is dependent upon a small number of nearshore nursery areas, including these lagoons. As such, conservation of lagoon habitats and monitoring of exploited fish stocks within them may be important for effective preservation of biodiversity within the catchment.     

Evolution of a cichlid fish in a Lake Malawi satellite lake

Allopatric divergence in peripheral habitats may lead to rapid evolution of populations with novel phenotypes. In this study we provide the first evidence that isolation in peripheral habitats may have played a critical role in generation of Lake Malawi's cichlid fish diversity. We show that Lake Chilingali, a satellite lake 11.5 km from the shore of Lake Malawi, contains a breeding population of Rhamphochromis, a predatory genus previously thought to be restricted to Lake Malawi and permanently connected water bodies. The Lake Chilingali population is the smallest known Rhamphochromis, has a unique male nuptial colour pattern and has significant differentiation in mitochondrial DNA from Lake Malawi species. In laboratory mate choice trials with a candidate sister population from Lake Malawi, females showed a strong tendency to mate assortatively indicating that they are incipient biological species. These data support the hypothesis that isolation and reconnection of peripheral habitats due to lake level changes have contributed to the generation of cichlid diversity within African lakes. Such cycles of habitat isolation and reconnection may also have been important in evolutionary diversification of numerous other abundant and wide-ranging aquatic organisms, such as marine fishes and invertebrates.     

Schistosomiasis in Lake Malawi: Relationship of Fish and Intermediate Host Density to Prevalence of Human Infection

Prior to 1985, the open waters of Lake Malawi were free from schistosome transmission. Over the past decades, however, the prevalence of urinary schistosomiasis has increased dramatically in the southern part of the lake. We found the prevalence of human schistosomiasis in school-aged children to be negatively correlated with the density of molluscivorous fishes. Specifically, the increased infection rate in southern Lake Malawi between 1978 and 1991 is coincident with the reduction in numbers of snail-eating fishes. During 2003, we determined the relative abundance of molluscivorous fishes and snail density at 18 sites throughout the lake and schistosome infection in school-aged children living in selected lakeshore communities of Lake Malawi. At the 18 sites sampled in 2003, we found that snail abundance decreased with an increase in abundance of snail-eating fishes. Furthermore, the 2003 samples showed that the abundance of snail-eating fishes increased and there was a reduction in schistosomiasis in school-aged children in Chembe Village. We believe that we will not observe a return to the 1978 infection rates until these fishes continue to increase and inhabit shallower waters.     

洱海流域水生态分区

分区边界的确定是生态分区的重要步骤,但目前多数水生态分区的边界确定以定性分析、专家判断为主。本研究以洱海流域为例,建立了一套两级分区体系。该体系基于GIS技术,用子流域作为分区基本单元,并用相关分析法,定量筛选一、二级分区指标。其中,一级分区指标为高程、坡度和植被归一化指数(NDVI),二级分区指标为农田百分比和城镇百分比。通过指标图层的叠加和重分类,合并同质性子流域,从而将洱海流域划分为5个一级区和9个二级区。藻类群落分布的验证结果表明分区合理。本研究将定量分析和子流域边界应用于水生态分区,使分区边界的确定更科学,在实际管理中更具有可操作性。本研究结果为水生态分区研究提供了新的方法,为洱海流域水生态管理提供了基本管理单元。