IMPACTS OF CALIFORNIA'S CLIMATIC REGIMES AND COASTAL LAND USE CHANGE ON STREAMFLOW CHARACTERISTICS1

ABSTRACT: To investigate the impacts of urbanization and climatic fluctuations on stream flow magnitude and variability in a Mediterranean climate, the HEC‐HMS rainfall/runoff model is used to simulate stream flow for a 14‐year period (October 1, 1988, to September 30, 2002) in the Atascadero Creek watershed located along the southern coast of California for 1929, 1998, and 2050 (estimated) land use conditions (8, 38 and 52 percent urban, respectively). The 14‐year period experienced a range of climatic conditions caused mainly by El Nino‐Southern Oscillation variations. A geographic information system is used to delineate the watershed and parameterize the model, which is calibrated using data from two stream flow and eight rainfall gauges. Urbanization is shown to increase peak discharges and runoff volume while decreasing stream flow variability. In all cases, the annual and 14‐year distributions of stream flow are shown to be highly skewed, with the annual maximum 24 hours of discharge accounting for 22 to 52 percent of the annual runoff and the maximum ten days of discharge from an average El Nino year producing 10 to 15 percent of the total 14‐year discharge. For the entire period of urbanization (1929 to 2050), the average increase in annual maximum discharges and runoff was 45 m³/s (300 percent) and 15 cm (350 percent), respectively. Additionally, the projected increase in urbanization from 1998 to 2050 is half the increase from 1929 to 1998; however, increases in runoff (22 m³/s and 7 cm) are similar for both scenarios because of the region's spatial development pattern.     

IMPACTS OF URBANIZATION ON NUTRIENT CONCENTRATIONS IN SMALL SOUTHEASTERN COASTAL STREAMS1

ABSTRACT: Coastal watersheds in the southeastern United States are rapidly changing due to population growth and attendant increases in residential development, industry, and tourism related commerce. This research examined spatial and temporal patterns of nutrient concentrations in streams from 10 small watersheds (< 4 km²) that drain into Murrells Inlet (impacted) and North Inlet (pristine), two high salinity estuaries along the South Carolina coast. Monthly grab samples were collected during baseflow during 1999 and analyzed for total and dissolved inorganic and organic forms of nitrogen and phosphorus. Data were grouped into forested wetland creeks (representing predevelopment reference sites), urban creeks, and urban ponds. DON and NH4 concentrations were greater in forested streams than in urban streams. NO3 and TP concentrations were greatest in urban streams. Seasonally, concentrations were highest during summer for TN, NH4, DON, and TP, while NO3 concentrations were greatest during winter. Nutrient ratios clearly highlighted the reduction in organic nitrogen due to coastal development. Multiple regression models to predict instream nutrient concentrations from land use in Murrells Inlet suggest that effects are not significant (small r²). The findings indicate that broad land use/land cover classes cannot be used to predict nutrient concentrations in streams in the very small watersheds in our study areas.     

基于元素流分析的长江经济带总磷污染减量化研究——以湖北为例

本文运用元素流分析方法,解析了长江经济带社会经济系统磷代谢的主要过程,构建了磷代谢分析框架及磷流核算模型,并以湖北为例,审视了其磷代谢过程及规律,定量识别了水体磷负荷的主要来源,力图提出减少长江经济带总磷污染的相关建议与对策。结果表明:(1)湖北长江经济带磷代谢系统整体结构不协调,呈现典型的单向型;(2)随着矿物磷—植物磷—动物磷的转换,重要工业化生产性子系统(磷化工、农业种植、规模养殖)磷的物质生产率逐渐退化,污染排放率、废物累积率、养分循环率则次第升高,城镇居民对总磷污染的贡献度要远超农村居民;(3)规模养殖、农业种植、磷化工、城镇居民生活是湖北长江经济带水体总磷污染的主要来源。     

广东省城镇化与生态环境耦合协调的空间特征及影响因素研究

为研究广东省快速城镇化与生态环境系统的相互影响关系,本文应用耦合协调度模型、地理探测器等方法对1995年、2005年、2016年广东省城镇化与生态环境耦合协调度及影响因素进行了分析。研究表明:①以广东省为研究区,1995—2016年广东省城镇化与生态环境耦合协调度呈持续上升趋势,整体呈S型曲线,经历了严重失调—中度协调—优质协调和城镇化滞后—相对平衡—生态环境滞后的过程。②以21个地级市为研究区,1995—2016年各地级市城镇化与生态环境耦合协调度持续提高,属优质和良好协调型的区域以珠海、深圳为核心逐步向外围扩展,表现出明显的核心—边缘特征。③生态环保政策、土地开发强度是不同时期影响21个地级市城市化与生态环境耦合协调度的共性因素。同时,2005年以前,产业结构及人口和GDP的快速增长是主要的影响因素;2005年以后,人口高度集聚、土地快速开发、科技和技术创新等因素则发挥着更重要的作用。     

FOREST COVER,IMPERVIOUS‐SURFACE AREA,AND THE MITIGATION OF STORMWATER IMPACTS1

ABSTRACT: For 20 years, King County, Washington, has implemented progressively more demanding structural and nonstructural strategies in an attempt to protect aquatic resources and declining salmon populations from the cumulative effects of urbanization. This history holds lessons for planners, engineers, and resource managers throughout other urbanizing regions. Detention ponds, even with increasingly restrictive designs, have still proven inadequate to prevent channel erosion. Costly structural retrofits of urbanized watersheds can mitigate certain problems, such as flooding or erosion, but cannot restore the predevelopment flow regime or habitat conditions. Widespread conversion of forest to pasture or grass in rural areas, generally unregulated by most jurisdictions, degrades aquatic systems even when watershed imperviousness remains low. Preservation of aquatic resources in developing areas will require integrated mitigation, which must including impervious‐surface limits, forest‐retention policies, stormwater detention, riparian‐buffer maintenance, and protection of wetlands and unstable slopes. New management goals are needed for those watersheds whose existing development precludes significant ecosystem recovery; the same goals cannot be achieved in both developed and undeveloped watersheds.     

碳中和的缘起、实现路径与关键科学问题：气候变化与可持续城市化

碳中和是我国应对气候变化的新目标,提出以来引起国内外广泛关注。碳中和目标实现是一个复杂系统科学问题,涉及大气圈、岩石圈、水圈、生物圈、人类圈等多圈层耦合过程与作用机制,需要跨学科交叉、综合与协同研究。简要梳理碳中和提出的气候变化和温控目标缘起,归纳碳中和实现的碳源、碳汇的多元路径,强调从碳源的需求侧推动可持续城市化对于碳中和目标实现的重要作用,并且可能是成本低、潜力大、更直接有效的方案途径。提出适应与减缓气候变化下碳中和与可持续城市化研究领域8个方面的科学问题：气候变化—碳中和—可持续城市化关联关系、中国及各地区碳中和实现的路线图与时间表、城市区域尺度碳排放的精准核算、绿色生活方式与低碳社会、绿色生产方式与低碳经济、能源结构优化、风险与不确定性和碳中和长效机制的治理创新等,以及该领域当前研究面临的机遇和挑战。     

新生代农民工市民化问题探析——基于生活满意度视角

新生代农民工市民化是我国当前重大社会问题,了解新生代农民工市民化的需求与驱动力对于促进其主动市民化,构建和谐社会具有重要意义。本文认为农民工市民化的过程就是其在城镇就业、定居进而构建并不断提高生活满意程度的过程,因而生活满意度是新生代农民工市民化的实质驱动力。利用四川省成都市的实地调查数据与实证分析,基于296份新生代农民工的问卷调查,采用多元回归分析技术,探讨了经济收入、社会福利、社会地位及社会关系等对新生代农民工生活满意度的影响程度。分析结果表明:新生代农民工具有追求平等、发展与融入城市的强烈愿望,其生活满意程度取决于经济收入、社会福利、社会地位及社会关系等方面与城市人的横向比较结果。最后提出了就业环境公平化、社会福利均等化及市民化教育等对策建议,从而有利于促进其从经济、社会到心理的城市融入。     

Problems of Rural Migrant Workers and Policies in the New Period of Urbanization

The huge migration of rural workers has new characteristics such as the bad order, high degree of concentration, low level of collective action, marginality in social status, unfair treatment, difficult integration of the new generation, and the new return trend of rural migrants, which causes ＇urban diseases＇ in China. Countermeasures should be taken to develop medium-sized and small cities, integrate the labor market of the city and countryside, provide necessary public services, social security and vocational training, guide the rural migrant workers to return rationally, and help the new generation live in harmony with urban residents.     

江苏省城市化战略调整研究

改革开放以来，江苏省城市化水平迅速提高，一直处于全国城市化发展的前列，对全国城市化水平的提高发挥了积极的示范作用。近些年来，江苏省城市化发展在空间格局及动力机制等方面出现了一些新的特征，表现为：大中城市成为城市化人口的主要集聚区，城市化的区域差异不断缩小，城市化发展动力也日趋多元化。同时，江苏省城市化仍然面临着区域差异显著、集聚效应不强、公共服务能力不高、资源环境压力较大等不可回避的问题。随着中国经济增长模式的转型，江苏省城市化战略将会发生适应性的调整。指出以城市土地空间扩张及城市数量增加为主的城市化道路已经基本不适应江苏省新时期新战略的要求，进而提出了今后一段时间全省城市化战略重点的调整方向，即质量提升战略、统筹协调战略及空间优化战略     

城镇化对太湖平原河网的影响——以太湖流域武澄锡虞区为例

为探讨近年来城镇化快速发展等对太湖流域腹部地区平原河网水系的影响，选取城镇化快速发展且城镇化程度很高的武澄锡虞区为例开展了研究。以1960年代、1980年代和2003年水系为基础，依据河道宽度对水系分级，并从河流地貌学角度定量分析了河网密度、水面率、河网复杂度、河网结构稳定度、分维数等结构特征及长时间序列的水位变化。结果表明：研究区水系要素基本上都在减小；不同等级的河流长度和河湖面积除一级河流面积增加外，均呈减少趋势。河网密度、水面率、分维数均变小，河网复杂度、河网结构稳定度下降，河网演化趋于主干化、单一化，河湖连通性下降。城镇化前后变化显著，且1980年代以来变化加快。同时城镇化背景下的水系衰减对河网蓄泄功能也产生了较大影响，使得年平均水位和汛期水位呈现上升趋势，导致洪灾风险增大。故在城镇化过程中应遵循河网演变规律，促进水系的保护