A Study of Temporal Variations of Groundwater Level, Recharge, and Baseflow: Does Scaling Exist in These Processes?

地下水位、补给和基流随时间变化的研究：这些过程中是否存在结垢？

• 批准号: 0510322
• 负责人: You-Kuan Zhang
• 金额: $ 23.59万
• 依托单位: University of Iowa
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-10-01 至 2009-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0510322&HistoricalAwards=false
• 关键词: Study; Temporal; Variations; Groundwater; Level

0510322ZhangGroundwater recharge (R) from precipitation and discharge to rivers as baseflow (BF) are two of the mainprocesses in the basin-scale water cycle. These processes vary with time and space. Effective managementof water resources requires deep understanding of these processes. Due to the lack of data or thedifficulties in measuring R and BF, however, our current knowledge and understanding of these complexprocesses are very limited, especially about their temporal and spatial variations. Various assumptions aremade about spatial variations of R in existing studies and little attention has been given to temporalvariations of R and BF. While it is difficult to measure R and BF, it is relatively easy to measure the waterlevels in observation wells (h) and runoff in rivers. Extensive groundwater level data sampled at varioustime intervals over periods of years or decades are often available. Fluctuations of the water table in agroundwater system are dynamic responses of the system to its recharge and discharge, and thus containsignificant amount of information about the recharge and discharge. Our preliminary analyses of theobserved water levels in seven monitoring wells at the Walnut Creek watershed of Iowa indicate thatfluctuations of the groundwater levels is a temporal fractal whose fractal dimension (D) varies spatially.Baseflow from this and other four watersheds also behaves as a temporal fractal and, more importantly,has a transition time or break in scaling.Our objectives are: 1) to determine existence of fractal scaling of groundwater level and baseflow andtheir relationship with recharge; 2) to identify physical causes behind fractal scaling; 3) to study the effectsof aquifers' physical heterogeneity on fluctuations of groundwater level, recharge, and discharge and ontheir scaling, and 4) to investigate the nature of groundwater recharge process. These objectives will bereached by testing six hypotheses. These hypotheses will be tested by collecting and analyzing the longtermgroundwater level measurements in 42 monitoring wells in 6 groundwater regions and thestreamflow at 58 gauge stations in 11 hydrological units over a period of 50 - 100 years at the USGGwebsite, and by conducting an integrated hydrologic modeling (IHM), stochastic analyses, and numericalsimulations. With data mining we will use the extensive data collected by USGS over the years to identifythe existence of the temporal scaling. With IHM we will be able to assess impacts of temporal and spatialvariations of P, ET, and ? on fluctuations of h and BF. With stochastic analyses and numericalsimulations, we will investigate effects of spatial variations of aquifers' physical properties on thetemporal variations of h and BF and their scaling as well as the nature of R process.The intellectual merits. The most important merits of this research are to find the temporal scaling of hand BF and to provide physical causes behind the scaling. Temporal scaling of h may be pervasive inmany aquifers as we show in this proposal by the spectra of the longest water level data in 14 USGS wells.There may be a simple explanation for the scaling: fluctuations of groundwater levels are due to variouscontributing hydrological variables (e.g., P, ET, and ?) with differing time and/or spatial scales. As aresult, there is no characteristic time scale in the head fluctuations! We are anxious to do furtherinvestigation. Whether processes in the natural world are dependent or independent of the scale at whichthey operate is one of the major issues in hydrologic science . (Sposito, 1998). There has been a significanteffort in searching for scaling in hydrology since an invariance property across scales as a fundamentalshould guide data analysis and modeling methods (NRC, 1991). Significant progresses in searching spatialscale invariance have been made during the last decade in hydrology. However, less attention was given totemporal scaling of subsurface hydrological variables. We have proposed a relatively new direction ofstochastic research, as summarized by the panel on the original proposal, and are trying to make a forwardstep in application of stochastic approaches. The broad impacts include: 1) use of abundant groundwaterlevel and streamflow data in trying to understand the patterns of temporal variations of h and BF make themethods and results of the proposed research widely applicable, 2) the proposed research is closely relatedto the NSF initiative: Water Cycle Research, 3) the knowledge obtained in this research is needed in longtermmanagement and planning of water resources and in dealing with climate changes, 4) A current Ph.D.student is working on this topic. Two new students (one graduate and one undergraduate) will participatein this project if the proposal is funded, 5) Several publications are expected from this research as twopapers have been written (one published and another submitted recently) based on our preliminary results.Finally, we want to say that addressing the comments made by the reviewers and panel on the original andsecond-submission of this proposal has greatly improved the proposal.

降水对地下水的补给和基流对河流的排泄是流域水循环的两个主要过程。这些过程随时间和空间而变化。水资源的有效管理需要深入了解这些过程。然而，由于缺乏数据或测量R和BF的困难，我们目前对这些复杂过程的知识和理解非常有限，特别是关于它们的时间和空间变化。现有的研究对R的空间变化作了各种假设，很少关注R和BF的时间变化。虽然R和BF很难测量，但测量观测威尔斯水位（h）和河流径流量相对容易。在几年或几十年的时间内，以不同的时间间隔采样的大量地下水水位数据往往是可用的。地下水位波动是地下水系统对补给和排泄的动态响应，包含了大量的补给和排泄信息。对爱荷华州核桃溪流域7口监测威尔斯观测水位的初步分析表明，地下水位的波动是一个时间分形，其分形维数（D）在空间上是变化的。来自该流域和其他四个流域的基流也表现为时间分形，更重要的是，有一个转换时间或尺度中断。我们的目标是：1）确定地下水位和基流分形标度的存在及其与补给量的关系：2）确定分形标度背后的物理原因;（3）研究含水层物理非均匀性对地下水位波动、补给和排泄及其标度的影响;（4）探讨地下水补给过程的性质。这些目标将通过测试六个假设来实现。这些假设将通过收集和分析USGG网站上6个地下水区域42个监测威尔斯井的长期地下水位测量值和11个水文单元58个水文站50 - 100年的径流量，并进行综合水文模型（IHM）、随机分析和数值模拟来检验。通过数据挖掘，我们将利用USGS多年来收集的大量数据来识别时间尺度的存在.与IHM，我们将能够评估的时间和spatialvariations的P，ET，和？h和BF的波动。通过随机分析和数值模拟，我们将研究含水层物理性质的空间变化对h和BF的时间变化及其标度的影响以及R过程的性质。本研究最重要的价值在于发现手部BF的时间尺度，并提供尺度背后的物理原因。h的时间标度在许多含水层中可能是普遍存在的，正如我们在本提案中通过14口USGS威尔斯井中最长水位数据的光谱所显示的那样。对这种标度可能有一个简单的解释：地下水位的波动是由于各种水文变量（例如，P、E、？具有不同的时间和/或空间尺度。结果表明，头部波动不存在特征时间尺度！我们渴望做进一步的调查。自然界中的过程是依赖于还是独立于其运行的尺度是水文科学的主要问题之一。（Sposito，1998年）。在水文学中，尺度的不变性是数据分析和建模的基础，因此尺度的研究是水文学研究的一个重要方面。近十年来，水文学在空间尺度不变性研究方面取得了重大进展.然而，较少注意到时间尺度的地下水文变量。我们提出了一个相对较新的随机研究方向，正如专家组对原始提案所总结的那样，并试图在随机方法的应用方面向前迈出一步。广泛的影响包括：1）利用丰富的地下水位和径流数据试图了解h和BF的时间变化模式，使所提出的研究方法和结果具有广泛的适用性，2）所提出的研究与NSF倡议密切相关：水循环研究，3）在这项研究中获得的知识是需要在长期管理和规划的水资源和应对气候变化，4）一位博士生正在研究这个课题。两位新同学（一个研究生和一个本科生）将参加这个项目，如果该建议得到资助，5）几个出版物，预计从这项研究，因为两个论文已经写了（一个已发表，另一个最近提交）根据我们的初步结果。最后，我们要说的是，在处理审查人员和专家组对原文件和第二份文件提出的意见时，这项建议的提出大大改善了这项建议。