太湖上游圩区氮磷管理的减污效益分析

太湖水体富营养化的重要驱动之一是流域上游区域的氮磷流失。圩区作为太湖上游平原区域的主要地理单元,具有复杂的水文与氮磷流失过程。针对圩区科学氮磷识别与高效管控是太湖治理的关键。本研究以太湖上游平原圩区为研究对象,采用氮动态模型（Nitrogen Dynamic model for lowland Polder systems,NDP）和磷动态模型（Phosphorus Dynamic model for lowland Polder systems,PDP）模拟圩区氮磷流失的动态过程,并基于圩区氮磷流失机制进行管理情景定量模拟与氮磷减污效益分析。结果表明：1）圩区氮磷的年平均流失强度分别为40和1.75 kg/ha/yr,高于太湖流域的平均氮磷流失水平;2）当圩区外部水质控制为Ⅳ类时,氮磷流失强度分别为37.54和1.58 kg/ha/yr,圩区截流氮磷量分别增加4.9%和9.9%,高氮磷流失级别的圩区数量分别减少26.2%和63.8%;3）如将圩区内5%的水田转化为水体,氮磷流失强度分别为36.73和1.72 kg/ha/yr,圩区截流氮磷量分别增加6.6%和1.7%,高氮磷流失级别的圩区数量分别减少46.2%和22.5%;4）圩区氮磷的流失机制具有明显不同,圩外水质目标对于圩内磷的流失影响较大,圩内的水体和坑塘等对于氮滞留和净化更加有优势。     

洞庭湖区堤垸耕地资源可持续性及其保护对策

从洞庭湖区堤垸人口、耕地资源时空特点入手,分析了堤垸耕地资源形成、发展变化趋势,耕地利用现状。洞庭湖区堤垸在“平垸行洪、退田还湖”的生态恢复建设和经济发展中,面临着人口不断增加,人均耕地减少;土地污染严重,耕地质量下降等问题。针对湖区社会、生态协调持续发展的原则,提出了6条堤垸耕地资源可持续性及其保护对策。(1)调整农业布局与种植制度,使耕地利用制度逐渐和耕地资源变化特点相吻合,保持耕地生态环境及其持续性。(2)据堤垸生态环境条件,采用避灾农业。(3)将水利基础设施建设列为国家保护农业生态环境重要内容之一。(4)加强对农业建设占用耕地的审批与管理。(5)加强环保意识,提高耕地质量。(6)积极推广节水灌溉技术。     

洞庭湖区景观格局变化及驱动力研究——以钱粮湖单退垸为例

基于洞庭湖1987、1996、2008年三期LANDSAT-TM影像及1∶10 000土地利用现状图,以钱粮湖单退垸为例,应用GIS技术及FRAGSTATS景观分析软件,从斑块类型和景观水平上分析了其近20多年来的景观格局动态变化,通过建立转移矩阵及计算转移贡献率,分析了景观格局变化的驱动力。结果表明:1987-2008年间,湖区景观要素类型发生了明显变化,总体上表现为旱地和园地面积持续减少,水域、水田、道路和建筑用地面积持续增加,林地面积先减后增;景观格局总体变化趋势是多样性增加、均匀度增加、破碎度增大、景观形状由简单趋于复杂;人口增长与城镇化建设、产业结构调整、退田还湖工程实施是导致研究区景观格局动态变化的三大驱动力。     

内河洪水对龙赛湖蓄滞洪区蓄洪容积影响特点的计算分析

蓄滞洪区的有效蓄洪容积是蓄滞洪区在分洪运用时实际能够蓄纳洪水的容积,是制定蓄滞洪区调度预案、实时优化调度方案的重要依据,内河洪水的调度将会占用蓄滞洪区内湖泊、圩垸及洼地的蓄洪容积,从而使有效蓄洪容积减少。选取汉北河龙赛湖蓄滞洪区,计算分析了不同频率内河洪水调度占用湖泊、圩垸及洼地蓄洪容积的变化特点,调蓄内河洪水后蓄滞洪区有效蓄洪容积的变化规律及影响,结果表明：①对于同时包括湖泊、圩垸和洼地的蓄滞洪区,调蓄内河洪水占用湖泊蓄洪容积显著大于占用圩垸及洼地蓄洪容积,内河洪水越大,占用湖泊与圩垸及洼地蓄洪容积的差别就越大。龙赛湖蓄滞洪区内河发生5年至50年一遇洪水时,在被占用蓄洪容积总量中,占用湖泊容积的比例达到97.9%~98.1%。②调蓄内河洪水减小蓄滞洪区有效容积随内河洪水频率的不同而改变,内河洪水越大,蓄滞洪区有效蓄洪的减小就越显著,龙赛湖蓄滞洪区内河发生50年一遇洪水时,有效蓄洪容积减小了约13.5%,而在发生5年一遇洪水时,有效蓄洪容积仅减小了7.81%。③当内河发生洪水并可能遭遇干流洪水时,蓄滞洪区有效蓄洪容积的减小将对干流防洪调度产生较为明显影响,应根据来水情况实时计算确定蓄滞洪区有效蓄洪容积,实时优化或调整调度方案,提前转移人员和财产。     

Drainage control in water management of polders in the Netherlands

One of the impacts drainage has on the downstream part of a water system is a higher risk of peak flows caused by heavy precipitation. In the polders of the Netherlands this is a well-known problem. The heavy precipitation flows easily from paved areas and with some delay from unpaved areas into many small canals and through these canals towards the downstream pump station. Here, high water levels can result in an unacceptable high groundwater table. This problem has grown over the past years as more area has been paved and storm events have become more extreme. Until recently in the Netherlands, the solution for this problem was to increase the pump capacity, but nowadays the Dutch Government's opinion and that of the local Water Boards about solving this problem is changing. Rather than shifting the problem to more downstream lying parts of the water system, the philosophy has become “first retain, then store, only then discharge” (Nationaal Bestuursakkoord Water, 2003. Dutch National Policy on Water Management for the 21st Century). A way to retain water in upstream parts of the waters system is to use real-time control structures in the upstream canals. In this paper a control method is presented that can effectively retain water in the upstream parts, until the downstream part can accommodate this amount of water. The method is based on upstream Proportional Integral-control with adaptation of the set point. The control is referred to as Cascade PI-Control. Basically, the goal of the control method is to fill the available storage equally in the whole area. Tests have been performed with a calibrated model of an existing polder in the Netherlands. Results show that application of the control method is sufficient to avoid such drainage problems.     

不受潮汐影响城镇圩区排涝泵站群常规调度方案优化

为降低不受潮汐影响城镇圩区排涝泵站群常规调度能耗,提出了排涝总能耗最小单目标选优和圩区内(外)河水位限制多目标去劣的优化方法。为圩区排涝泵站群常规调度确定若干种典型排水条件组合,对每组排水条件,以泵站为试验因素、各泵站不同的运行规则为试验水平、不同运行规则组合下的最小运行能耗为试验结果开展正交试验;对试验结果开展正交分析获得各泵站从优到劣不同运行规则组合序列。对每组运行规则序列,根据各泵站排水能力限制,应用动态规划法可获得圩区泵站群最低排涝能耗及对应的各泵站开机方案;对最低排涝能耗排序可获得圩区泵站群优化运行方案序列,进一步应用圩区内(外)河水位限制条件可获得圩区泵站群某排水条件下最优调度方案。以上海市城区某区域为实例,阐明了优化计算全过程,优化计算结果比现行调度方案的排涝能耗至少可节省6%。