PREFERENTIAL FLOW (PF) PATTERNS IN DIFFERENT SOIL-LANDSCAPES

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 1010232
• Project Start Date: Jul 5, 2016
• Project End Date: Feb 26, 2020
• Program Code: [(N/A)]- (N/A)

Recipient Organization
PENNSYLVANIA STATE UNIVERSITY
208 MUELLER LABORATORY
UNIVERSITY PARK,PA 16802

Performing Department
Ecosystem Science & Management

Non Technical Summary
Preferential flow (PF) is a fundamentally important hydrologic process that influences a variety of earth surficial processes. However, PF quantification and prediction remain notoriously elusive. This project seeks to break through this bottleneck by advancing two important fronts: 1) A practical means of detecting and quantifying PF across diverse soil-landscapes, and 2) A new conceptualization of dynamic PF networks embedded in the soil-landscape mosaic. We hypothesize that, while the potential for PF to occur in real-world soils is ubiquitous, it takes the right combination of soils and environmental conditions for PF to actually happen. The controls of PF occurrence can be grouped into site factors (including landform unit and soil type) and temporal factors (including initial soil moisture, precipitation characteristics, and plant growth stage). A framework for classifying these key controls can offer a means of estimating the frequency of PF occurrence in diverse soil-landscapes. We further hypothesize that a dynamic PF flow network embedded in the subsurface resembles (to some extent) an ephemeral stream-like network, which is governed by a dual-flow regime, i.e., water follows through the least-resistant or preferred paths when "pushed" (e.g., by storms) or "attracted" (e.g., by plants) or "restricted" (e.g., by impermeable layers), but moves diffusively into the matrix when "relaxed" (e.g., through capillarity) or "touched" (e.g., via adsorption).We will use extensive real-time soil moisture monitoring databases to investigate the condition, timing, frequency, and mechanism of PF occurrence in diverse soil-landscapes. Six large existing and continuously-expanding databases from the U.S., Germany, and China have been selected for use in this project. These databases are among the most comprehensive ones currently available in the world. High-density and multiple depth soil moisture monitoring datasets will be systematically analyzed to identify soil moisture response signatures to precipitation events and to identify various flow scenarios and related mechanisms. A set of MATLAB tools (called the Hydropedograph Toolbox) has been developed from our previous work that can be used for efficient and consistent analysis of soil moisture time series profiles, including the determination and visualization of PF and related controls. This toolbox will be further enhanced to provide batch processing of spatially-distributed sites across a landscape and to facilitate site comparisons. Frequency and timing of PF occurrence and related controls will be summarized for all monitoring sites to reveal subsurface flow networks and their relationships with the five identified main controls. These relationships will then be synthesized into a framework for estimating PF occurrence in various soil-landscapes.

Animal Health Component

20%

Research Effort Categories

Basic

80%

Applied

20%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
102	0110	2050	100%

Knowledge Area
102 - Soil, Plant, Water, Nutrient Relationships;

Subject Of Investigation
0110 - Soil;

Field Of Science
2050 - Hydrology;

Keywords

preferential flow

soil moisture

soil hydrology

soil physics

soil-landscape

Goals / Objectives
The objective of this project is to address a long-standing need in the hydrologic sciences: To detect and quantify PF occurrence frequency and its major controls in diverse soil-landscapes. Specifically, we propose to test the following two interlinked hypotheses:H1 While the potential for PF to occur in field soils is ubiquitous, it takes the right combination of soil-landscapes (media, internal factors) and environmental conditions (drivers, external factors) for PF to actually happen. These controls can be grouped into site factors (including landform unit and soil type) and temporal factors (including initial moisture, precipitation, and plant growth). The occurrence frequency and dominant mechanism of PF may be estimated based on a framework that characterizes these five major factors in relation to PF occurrence. A draft of this framework has been developed and will be further developed and tested in this project using large (in both spatial and temporal coverage) existing soil moisture databases from various climatic regions;H2 Preferential flow generally occurs as a complex and dynamic flow network embedded in the soil-landscape mosaic. Despite its complexity, it exhibits an overall pattern that resembles (to some extent) a stream-like network. This is because water generally follows the least-resistant or preferred paths when "pushed" (e.g., by storms) or "attracted" (e.g., by plants) or "restricted" (e.g., by low permeable layers), but moves diffusively into the matrix when "relaxed" (e.g., through capillarity) or "touched" (e.g., via adsorption). Such a network-like PF pattern may be detected from spatially densely-distributed real-time soil moisture monitoring networks. This will be further investigated in this project using the Hydropedograph Toolbox and large existing soil moisture monitoring databases from diverse soil-landscapes.

Project Methods
This project will use extensive field soil moisture monitoring databases to investigate the condition, timing, frequency, and mechanism of PF occurrence across a wide range of soil-landscapes. At the present, six large databases from the U.S., Germany, and China have been selected for use in this project. The criteria for choosing these databases include: 1) All the networks have densely-spaced automatic soil moisture monitoring stations within small catchments, with reliable, high temporal resolution, and continuously-expanding databases suitable for testing the proposed hypotheses in this project; 2) These monitoring networks cover a wide variety of soil types, landform units, and environmental conditions (climate and land use) that are linked to the five key controls of PF occurrence to be tested in this project, hence providing ample scenarios to comprehensively examine PF flow cases and to develop the envisioned framework for estimating the occurrence frequency and dominant controls of PF in diverse soil-landscapes; 3) These databases are among the most comprehensive ones currently available in the world, with considerable spatial and temporal coverage as well as ancillary datasets for in-depth investigations of soil-landscape properties (including climate, stream discharge, groundwater, terrain attributes, soil maps and properties, subsurface geophysical surveys, and others); and 4) I have already established good working relationships with the collaborators involved.Testing the H1: Fundamental Relationships between PF Occurrence and Its Main ControlsKey factors controlling PF occurrence will be comprehensively investigated in this project for each of the study areas, which will then be organized into an overarching framework. The key controls identified are based on our previous studies, including:Precipitation characteristics: such as amount, intensity, duration, and timing;Initial soil moisture: moisture content in various horizons/depths and proceeding days' precipitation;Land use/land cover: such as vegetation type, plant growth stage/season, and management practices;Landscape features: such as landform, hillslope type/shape, slope, and underlying bedrock;Soil conditions: including soil type, horizonation, texture, structure, and other soil properties.We plan to use our existing Hydropedograph Toolbox (version 1) to identify and quantify PF occurrence in the selected study areas. This Toolbox contains various modules that permit an efficient and consistent analysis of multi-depth soil moisture time series data within a soil profile, including the determination and visualization of PF occurrence and related key soil hydrologic properties. However, this toolbox is currently suited for analyzing one monitoring location at a time. Therefore, this toolbox will be enhanced through this project to provide batch processing for many spatially-distributed sites across a catchment and to provide new functionality for cross-site comparisons. We also plan to link soil-landscape features into the toolbox so that soil-landscape controls on PF occurrence can be better identified. We will also add new time series analysis to expand the toolbox's capacity to detect patterns and trends at various time scales.The Hydropedograph Toolbox is currently designed to analyze a soil profile consisting of synchronous soil moisture measurements at multiple depths. Required data include time series of soil moisture of high enough temporal resolution and duration and with multiple depths (≥ 3) within a soil profile. Soil moisture is examined after each precipitation event, and the sequence of soil moisture sensor response at various depths will be classified as either 1) sequential or 2) out-of-sequence response. Intuitively, rainwater should infiltrate into the soil surface first and then pass an upper depth before it can reach a lower depth. When a soil moisture sensor in a subsoil responds to a rainfall event earlier than a sensor located above it (called out-of-sequence response), then it is reasonable to infer that rainwater has 1) either vertically bypassed the overlying soil and/or 2) laterally percolated into the deeper subsoil from surrounding upslope or sideslope area. In either case, a PF of rainwater has occurred, and this can be picked up by real-time soil moisture monitoring.Testing the H2: Dynamic PF Networks Embedded in the Soil-Landscape MosaicWe will address the following three overarching questions to guide this task:Does a subsurface PF network exist in each of the study areas? If so, to what extent does it resemble a stream-like network pattern?What are key controls in different soil-landscapes that contribute to such subsurface PF network pattern?How does subsurface PF network pattern change over time in response to initial moisture or season, precipitation characteristics or type of storm, and plant growth stage or species?We will first delineate a series of storm events based on precipitation time series data for each of the study areas, and then will analyze the response to each of these individual precipitation events by each soil moisture sensor installed at different depths at each monitoring site. The out-of-sequence soil moisture response to precipitation will be first identified and then carefully analyzed for identifying processes involved. While sequential but rapid response to precipitation could be another characteristic of PF, such behavior can also be due to differences in pressure response and wave propagation (Rasmussen et al., 2000; Torres and Alexander, 2002) or simply high soil matrix permeability. Due to the uncertainty in this type of situation, rapid sequential soil moisture response to precipitation inputs will not be included in our statistical summary for PF in this project (but such results will be generated and reported separately). For this reason, our results will establish a confident minimum frequency of preferential flow.Various flow scenarios and related underlying mechanisms, as described in our new conceptualization, will be identified and then summarized for each study area. This is to be accomplished by careful and systematic interpretations of 1) the sequence of soil moisture response time within the same profile during each precipitation event and 2) the shape and slope of wetting and drainage curves at different soil depths. Such interpretation has been successfully applied in our early work.The densely-spaced soil moisture monitoring networks in small catchments provide the possibility of connecting the "dots" (point observations) to infer subsurface PF networks, as illustrated in our early study (Liu and Lin, 2015). Such a subsurface network routes rainwater downslope in a dynamic manner, and is initiated more readily as rain intensifies, especially during wet seasons (Graham and Lin, 2011). Threshold rainfall, critical soil layering control, macropores of various kinds, hydrophobicity, concave topography, and fractured bedrock, all have been identified in our study as important contributors to forming PF networks (Lin, 2006; Lin and Zhou, 2008; Liu and Lin, 2015). We will summarize PF occurrence frequency at all monitoring sites in each of the study areas, and then will generate a map for each catchment to test the H2 hypothesis.With a PF map completed for each catchment, we can then examine its possible similarities to a stream network, including their overall patterns and specific network parameters (e.g., Forman, 1995). We can also answer the second and third overarching questions by 1) comparing PF occurrence frequency at each monitoring site with maps of soil-landscape attributes in each catchment and 2) grouping PF occurrence frequency by different initial moisture conditions, precipitation events, and plant growth seasons.

Progress 07/05/16 to 02/26/20

Outputs
Target Audience:Researchers, educators, students, and practitioners who are interested in the interface between soil science and hydrology and other related bio- and geo-sciences. Changes/Problems:Lead PI Henry Lin deceased on September 26, 2019. What opportunities for training and professional development has the project provided?Three postdocs (Hu, Bihang, and Li) and two graduate students (Haoliang, Yuan) who have worked on this project have each obtained a professional job in China working in the areas of soils and hydrology. One collaborator of this project (Gregory) has received the tenure and promotion from Assistant Professor to Associate Professor. More than thirty visiting scholars from China, Europe, and other institutions in US as well as five REUs from Penn State and Indiana University of Pennsylvania were trained to work with and maintain the soil moisture sensor network and use the Hydropedography Toolbox for PF analysis using the real-time soil moisture monitoring data. How have the results been disseminated to communities of interest?PI Lin hosted the 3rd International Conference on Hydropedology, which included PF as a theme. Project participants Guo and Fan presented in this conference. PI Lin and project participant Guo co-chaired a PF session in 2016 AGU fall meeting and an Eco-hydrological modelling session 2016 International Society of Ecological Modeling. PI Lin and project participants Guo and Tang presented PF study progress in 2017 and 2018 AGU fall meeting and the all-hands meeting of Critical Zone network (CRITICAL ZONE SCIENCE Current Advances & Future Opportunities) in Arlington, VA. PI Lin and project participant Guo hosted a seminar on Penn State campus to introduce the advance of PF study and its key role in Critical Zone science to delegates from the Chinese Geologic Survey. (http://criticalzone.org/shale-hills/news/story/delegation-from-china-geologic-survey-visits-shale-hills-czo/) Participant Guo was invited to give a talk on using geophysical tools and soil moisture sensor network to detect and quantify PF across scales in The 2017 Field Conference of Pennsylvania Geologists and Penn State Extension Annual Conference. (https://criticalzone.org/shale-hills/news/story/water-resources-extension-educators-tour-the-czo/; http://criticalzone.org/shale-hills/news/story/82nd-annual-field-conference-of-pa-geologists-tour-the-czo/) Our paper (Guo and Lin, 2016, Vadose Zone J) was featured by the Alliance of Crop, Soil, and Environmental Science Societies as research highlights (https://dl.sciencesocieties.org/story/2016/oct/wed/critical-zone-research-and-observatories-current-status-and-future-perspectives) PI Lin was featured in the Germany's TERENO Newsletter for his involvements including his work on the preferential flow. Colleagues from US, Europe, and China have visited us to discuss collaborations on PF studies. Project participant has been invited to review two preferential flow related proposals, one submitted to the US NSF Hydrologic Sciences Program and the other submitted to the Dutch Research Council. Project participant has been invited to give a talk in Sichuan University and Northeast Normal University in China to introduce the progress in preferential flow research. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? This project has demonstrated clear two-way interactions between PF and soil structure and many subsurface processes, such as soil moisture distribution and variation, physical translocation of materials, and root water uptake. The framework of major controls of PF that we developed has been further refined and is used to guide the prediction of the susceptibility of various soils and landscapes to PF. We confirmed our hypothesis that PF occurs when rainfall water is "pushed" (e.g., by storms) or "attracted" (e.g., by plants) or "restricted" (e.g., by low permeable layers), but moves diffusively into the matrix when "relaxed" (e.g., through capillarity) or "touched" (e.g., via adsorption). We have 15 papers published that are closely related to the topic of preferential flow with 9 of them acknowledging the NIFA Support in the publication. Five additional under review or in preparation. We have established four databases of real-time soil moisture monitoring networks, including the forested Shale Hills Catchment in Pennsylvania (data covering 2011-2019), a forested catchment in Germany from the Terrestrial Environmental Observatories (2008-2019), a pair of catchments (one covered by forest and the other by grass) on the Chinese Loess Plateau (2016-2019), and a pair of catchments (one mountainous forested catchment and one cropped catchment) in the middle reaches of the Changjiang River (2016-2019). We have refined the quantification of the frequency of PF occurrence and its controls through the use of high-frequency and high-density soil moisture sensor networks. We have developed the Hydropedography Toolbox Version 2 for the analysis of the real-time soil moisture monitoring data, including PF identification and quantification and the spatiotemporal analysis of soil moisture distribution, trend, and its response to precipitation. This toolbox will be made freely available to the scientific community after completion. A manuscript with detailed description of this toolbox has been developed and will be submitted to the Journal of Hydrology. We have enhanced field mapping and monitoring of PF pathways and dynamics, such as combining multiple geophysical techniques, combining time-lapse geophysical investigation with infiltration experiments, dye injection, thermal imaging, and high-frequency soil moisture monitoring, and improving geophysical data processing and image analyzing skills to identify PF signatures in geophysical images, thermal images, and optical images. We have proposed the "3D fill-and-spill model" for subsurface PF at the hillslope and catchment scales. This model describes the role of different types of PF in subsurface hydrology and water flux through the Critical Zone, which has the potential toward a generalizable characterization and modeling of hillslope/catchment hydrology. According to a series of studies on PF generation, dynamics, duration, magnitude and spatial distribution in various environments, we have established a framework to summarize the dominant controls of PF across a wide variety of soils and landscapes and improved the understanding of the two-way interactions between PF and soil structure and many subsurface biogeochemical processes, such as soil moisture distribution and variation, physical translocation of materials, and landscape evolution.

Publications

• Type: Journal Articles Status: Awaiting Publication Year Published: 2020 Citation: Guo L, Mount G, Hudson S, Lin H, Levia D (2020). Pairing geophysical techniques improves understanding of the near-surface Critical Zone: visualization and confirmation of preferential routing of stemflow along coarse roots. Geoderma, online published. doi:10.1016/j.geoderma.2019.113953
• Type: Journal Articles Status: Published Year Published: 2019 Citation: Zhang S, Hopkins I, Guo L, Lin H (2019). Dynamics of infiltration rate and field-saturated soil hydraulic. Water, 11: 1632. doi:10.3390/w11081632
• Type: Journal Articles Status: Published Year Published: 2019 Citation: Guo L, Lin H, Fan B, Nyquist J, Toran L, Mount G (2019). Preferential flow through shallow fractured bedrock and a 3D fill-and-spill model of hillslope subsurface hydrology. Journal of Hydrology, 576:430-442. doi:10.1016/j.jhydrol.2019.06.070
• Type: Journal Articles Status: Published Year Published: 2019 Citation: Jin Z, Guo L, Wang Y, Yu Y, Lin H, Chen Y, Chu G, Zhang J (2019). Effects of dams and reservoirs on soil salinization in the reshaped creek valley on the Chinese Loess Plateau. Geoderma, 339: 115-125. doi: 10.1016/j.geoderma.2018.12.048

Progress 10/01/17 to 09/30/18

Outputs
Target Audience:Researchers, educators, students, and practitioners who are interested in the interface between soil science and hydrology and other related bio- and geo-sciences Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Ten (10) visiting scholars from China were trained in my lab to conduct data download and equipment maintenance in the field. They were also trained to use the Hydropedography toolbox for PF analysis using the real-time soil moisture monitoring data. The project results are also used in classroom teaching for Soils 405 Hydropedology course. How have the results been disseminated to communities of interest? PI Lin and project participant Guo attended a PF session in 2017 AGU fall meeting and the national all-hands meeting of the Critical Zone network (CRITICAL ZONE SCIENCE Current Advances & Future Opportunities) hosted by NSF in June 2018 in Arlington, VA. PI Lin and project participant Guo hosted a seminar on Penn State campus to introduce the advance of PF study and its key role in Critical Zone science to 15 delegates from the Chinese Geologic Survey. We also gave a talk on using geophysical tools and soil moisture sensor network to detect and quantify PF across scales in The 2017 Field Conference of Pennsylvania Geologists and Penn State Extension Annual Conference Five papers are to be presented at the upcoming AGU fall meeting in Washington DC What do you plan to do during the next reporting period to accomplish the goals?We plan to revise the following manuscripts and get them published: Lin, H.S., L. Guo, X. Li, H. Bogena, P. Groffman, H. Gerke, K. McGuire, A. O'Geen, M. Sommer, K. Vaughan, and H.J. Vogel. 2018. Advances in hydropedology - A decadal review. Advances in Agronomy (in review) Guo L, Fan B, H.S. Lin*, Nyquist J, Toran L, Mount G. 2018. Preferential flow through shallow fractured bedrock in the Shale Hills Critical Zone Observatory. Water Resource Research (in review) Guo L., Mount G., Hudson, S., D. Levia*, H.S. Lin*. 2018. Linking stemflow and subsurface preferential flow by geophysical investigation. Geophysical Research Letter (in review) Zheng H., H.S. Lin*, W. Zhou, H. Bao, X. Zhu. 2018. Spatial and temporal variation in terrestrial water use efficiency during 2000-2014 in China's Loess Plateau: Evidence from satellite data. Agricultural and Forest Meteorology (in review) Jin, Z.*, H.S. Lin*, L. Feng, L. Guo, Y. Wang. 2018. The evolution of loess tablelandsin the Chinese Loess Plateau: A fragmentation process accelerated by human activities. Earth Surface Processes and Landforms (in review) In addition, we plan to do accomplish the following in the next reporting period: More soil moisture and GPR/EMI data are to be collected to advance the detection and quantification of PF in the field. Refine the field method of detecting PF by coupling thermal imaging and time-lapse GPR scanning. Upscale PF patterns from the site-scale to hillslope/catchment-scale hydrologic behaviors.

Impacts
What was accomplished under these goals? This project has demonstrated clear two-way interactions between PF and soil structure and many subsurface processes, such as soil moisture distribution and variation, physical translocation of materials, and root water uptake. The framework of major controls of PF that we developed has been further refined and is used to guide the prediction of the susceptibility of various soils and landscapes to PF. We confirmed our hypothesis that PF occurs when rainfall water is "pushed" (e.g., by storms) or "attracted" (e.g., by plants) or "restricted" (e.g., by low permeable layers), but moves diffusively into the matrix when "relaxed" (e.g., through capillarity) or "touched" (e.g., via adsorption). This leads to a network-like PF pattern that has been detected from spatially densely-distributed real-time soil moisture monitoring networks. The Hydropedograph Toolbox has been further refined, which is to be made freely available to the scientific community after completion. We have published 10 peer-reviewed journal articles during this period. These have added new understandings on the dynamics and controls of PF occurrence across various soil-landscapes. For example, our paper (Gu et al., 2018) has been selected (because of its significance and impacts) for promotion in CSA News and its social media for the Agronomy, Crop Science, and Soil Science societies (i.e., CSSA, SSSA, and ASA). This paper addresses the fundamental theory of hillslope/catchment hydrology and clearly highlights the importance of hydropedological factors in generating PF and the hydrological maze (i.e., puzzles, paradoxes, or complexity involved in hydrologic measurements and interpretations). Stakeholders from industry (e.g., Dr. Ehsan Toosi at Actagro, LLC in Biola, CA) also benefited from our work. For example, Dr. Toosi wrote to us about our paper (Lin and Guo, 2018), stating that our work is helpful in their current efforts to reduce nitrate leaching, and indicated that our work is cited in their upcoming book chapter. Furthermore, Russian scientist Lisetskii Fedor (a senior professor at Belgorod State National Research University, Dept. of Natural Resources and Land Management, and Director of the Federal-regional center of aerospace and surface monitoring of natural resources) wrote to me out of the blue, stating that my paper published a few years ago (Lin, H.S. 2011. Soil Science Society of America Journal 75:2049-2070) is the best work among those that were published in the last 10-20 years. He himself has cited my paper multiple times in his several recent publications. Another noticeable accomplishment is a special issue of Vadose Zone Journal, entitled "Frontiers in Hydropedology: Interdisciplinary Research from Soil Architecture to the Critical Zone" has been completed. I am one of three co-guest editors of this special issue. This accomplishment has advanced interdisciplinary science of hydropedology and its impacts on integrated soil and water resources management. This has contributed to the growing interests among national and international scholars and stakeholders in hydropedology and related Critical Zone science.

Publications

• Type: Journal Articles Status: Published Year Published: 2018 Citation: Guo L, H.S. Lin. 2018. Addressing Two Bottlenecks to Advance the Understanding of Preferential Flow in Soils. Advances in Agronomy, 147:61-117
• Type: Journal Articles Status: Published Year Published: 2018 Citation: Guo, L. B. Fan, J. Zhang, and H.S. Lin*. 2018. Subsurface lateral flow in the Shale Hills Catchment as revealed by a soil moisture mass balance method. European Journal of Soil Science 67:771-786.
• Type: Journal Articles Status: Published Year Published: 2018 Citation: Nyquist J., Toran L, Pitman L, Guo L, H.S. Lin. 2018. Testing the Fill-and-Spill Model of Subsurface Flow Using GPR and Dye Tracing. Vadose Zone Journal 16:1-12. doi: 10.2136/vzj2017.07.0142.
• Type: Journal Articles Status: Published Year Published: 2018 Citation: Gu, W.Z., J.F. Liu, H.S. Lin, H.W. Liu, A.M. Liao, N. Wang, W.Z. Wang, T. Ma, N. Yang, X.G. Li, P. Zhuo, Z. Cai. 2018. Why hydrological maze: The hydropedological trigger?  A review of experiments from natural and artificial catchments at the Chuzhou Hydrology Laboratory. Vadose Zone Journal 17:170174. doi:10.2136/vzj2017.09.0174.
• Type: Journal Articles Status: Published Year Published: 2018 Citation: Li, X., H.S. Lin, and H. Gerke. 2018. Frontiers in Hydropedology: Interdisciplinary Research from Soil Architecture to the Critical Zone. Vadose Zone Journal 17
• Type: Journal Articles Status: Published Year Published: 2018 Citation: van der Meij, W.M., A.J.A.M Temme, H.S. Lin, H.H. Gerke, M. Sommer. 2018. On the role of hydrological processes in soil and landscape evolution modeling: Concepts and complications for structured soils. Earth-Science Reviews 185:10881106.
• Type: Journal Articles Status: Published Year Published: 2018 Citation: Fu, W., Y. Shao, C. Pang, Y. Zhang, X. Huang, X. Zeng, M. Yang, and H.S. Lin. 2018. Garnierite mineralization from a serpentinite-derived lateritic regolith, Sulawesi Island, Indonesia: Mineralogy, geochemistry and link to hydrologic flow regime. Journal of Geochemical Exploration 188:240256.
• Type: Journal Articles Status: Published Year Published: 2018 Citation: Tao, W.H., Q.J. Wang, H.S. Lin. 2018. Approximated analytical solutions for describing surface runoff and sediment transport over hillslope. Journal of Hydrology 558:496508.
• Type: Journal Articles Status: Published Year Published: 2018 Citation: Liu M.X., Guo L., Yi J., H.S. Lin, Lou S., Zhang H., Li T. 2018. Dye tracer experiments to characterize preferential flow and its interaction with the soil matrix in the Three Gorges Reservoir Area of China. Soil Research 56:588-600.
• Type: Journal Articles Status: Published Year Published: 2018 Citation: Jin, Z., L. Guo, H.S. Lin, Y. Wang, Y. Yu, G. Chu, J. Zhang. 2018. Soil moisture response to rainfall on the Chinese Loess Plateau after the long-term vegetation rehabilitation. Hydrological Processes 32:1738-1754.

Progress 10/01/16 to 09/30/17

Outputs
Target Audience:Researchers, educators, students, and practitioners in the areas of soil science and hydrology. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?We have used the Shale Hills Critical Zone Observatory and two other landscapes near Penn State in classroom teaching and meeting field trips. We have also offered training and professional development opportunity for several graduate and undergraduate students at Penn State as well as five visiting scholars from China. How have the results been disseminated to communities of interest?Project results have been disseminated in the following invited presentations: Lin, H.S. 2017. Critical Zone Science and Three Principles of Water Flow in Soils. Invited seminar at Chang'an University, Oct. 10, 2017, Xi'an, China. Lin, H.S. 2017. Green water: Essential in combating looming global freshwater crisis. Invited talk at the 2017 Chinese Soil Physics Biannual Conference, Shengyang, China Aug. 3-5, 2017. Lin, H.S. 2017. Soil Moisture: Green Water: Essential in Combating Global Freshwater Crisis. The 2017 Workshop at MOISST: Integrating Diverse Sources of Soil Moisture Information. May 23-25, 2017. Oklahoma State University, Stillwater, Oklahoma. What do you plan to do during the next reporting period to accomplish the goals?We plan to revise the following manuscripts and get them published: Guo, L. B. Fan, J. Zhang, and H.S. Lin. 2018. Subsurface lateral flow in the Shale Hills Catchment as revealed by a soil moisture mass balance method. European J. of Soil Sci. (in review) Nyquist, J.E., L. Toran, L. Pitman, L Guo, and H.S. Lin. 2018. Testing the Fill-and-Spill Model of Subsurface Flow Using GPR and Dye Tracing. Vadose Zone Journal (in revision) Jin, Z., Li Guo, H.S. Lin, Yunqiang Wang, Yulong Yu, Guangcheng Chu, Jing Zhang. 2017. Effects of afforestation and natural revegetation on soil moisture dynamics in paired watersheds in the Loess Plateau of China. Hydrological Processes (in review) Zhao, Y, Y. Wang, L. Wang, X.Zhang, Y. Yu, Z. Jin, H.S. Lin, Y. Chen, W. Zhou, Z. An. 2018. Effects of land restoration on soil water in the hilly-gully region of the Chinese Loess Plateau. Ecological Engineering (in revision) Lin, H.S., L. Guo, X. Li, H. Bogena, P. Groffman, H. Gerke, K. McGuire, A. O'Geen, M. Sommer, K. Vaughan, and H.J. Vogel. 2018. Advances in hydropedology - A decadal review. Advances in Agronomy (in review)

Impacts
What was accomplished under these goals? Preferential flow (the phenomenon where fluid, gas, and/or chemicals move through preferred pathways in a porous medium such as soils, thereby bypassing large portions of a porous system) has significant impacts on water quality, soil health, ecosystem services, hydrologic cycle, and contaminant fate in the environment, thus preferential flow in soils has become a crucial issue in both scientific community and soil-water resources management. Through this research project, we have synthesized key aspects in understanding, predicting, and managing preferential water flow in soils, including those in forest catchments and agricultural fields. Dominant controls of preferential flow occurrence in various soils and landscapes have been synthesized into a framework with six key categories of controls (a. soil architecture, b. soil properties, c. landscape setting, d. land use/land cover, e. seasonal soil wetness conditions, f. precipitation/irrigation characteristics), which is practically transferable to management practices. Reprints of our published papers have been requested at least 10 times by fellow researchers around the U.S. (including government agencies such as USDA) and globally (China and Germany) as well as interested stakeholders from industry (e.g., Dr. Ehsan Toosi at Actagro, LLC in Biola, CA). Furthermore, our innovative use of soil sensor networks and geophysical techniques for quantifying preferential flow in the field has led to the development of new tools that can be used to detect and monitor preferential flow in the real world.

Publications

• Type: Journal Articles Status: Published Year Published: 2017 Citation: Guo, L. and H.S. Lin. 2017. Addressing Two Bottlenecks to Advance the Understanding of Preferential Flow in Soils. Advances in Agronomy https://doi.org/10.1016/bs.agron.2017.10.002.
• Type: Journal Articles Status: Published Year Published: 2017 Citation: Baldwin, D., K.J. Naithani, and H.S. Lin. 2017. Integrated soil-terrain stratification for characterizing catchment-scale soil moisture variation. Geoderma 285:260-269.
• Type: Journal Articles Status: Published Year Published: 2017 Citation: Duncan, E.W., P.J.A Kleinman, G.J. Folmar, L. Saporito, G.W. Feyereisen, A.R. Buda, L. Vitko, A. Collick, P. Drohan, H.S. Lin, R.B. Bryant, and D.B. Beegle. 2017. Field scale lysimeters to assess nutrient management impacts on runoff. Transactions of the ASABE 60:419-429.
• Type: Journal Articles Status: Published Year Published: 2017 Citation: Ma, Y., X. Li, L. Guo, and H.S. Lin. 2017. Hydropedology: Interactions between Pedologic and Hydrologic Processes across Spatiotemporal Scales. Earth Science Review 171:181-195.

Progress 07/05/16 to 09/30/16

Outputs
Target Audience:Researchers, educators, students, and practitioners in the areas of soil science and hydrology. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?We have used the Shale Hills Critical Zone Observatory and two other landscapes near Penn State in Soils 405 (Hydropedology) and Soils 507 (Environmental Soil Physics) classroom teaching and field trips. We have also offered training and professional development opportunity for four graduate students and three undergraduate students at Penn State as well as five visiting scholars from China. How have the results been disseminated to communities of interest?Project results have been disseminated in the following invited presentations: Lin, H.S. 2016. Soil and Water Resources: Tackling the Last Hydrologic Frontier. An invited talk at the workshop of Soils -- The Foundation of Life by the U.S. National Committee for Soil Sciences, National Academies of Sciences, Engineering, and Medicine, Dec. 5, 2016. Washington, DC. Lin, H.S. 2016. Hot Spots and Hot Moments: Linking Hydropedology and Biogeochemistry in the Critical Zone. AGU Fall meeting, 2016, San Francisco, CA. What do you plan to do during the next reporting period to accomplish the goals?We plan to summarize main controls of preferential flow occurrence across various soils and landscapes using real-time soil moisture monitoring datasets and the published literatures, and intend to publish a synthesis paper on the spatial-temporal pattern of preferential flow occurrence.

Impacts
What was accomplished under these goals? Three journal articles have been published. We have enhanced quantitative assessment of the frequency and control of preferential flow occurrence across three different soil-landscapes in central Pennsylvania. Our work has shed light on the initiation and persistency of preferential flow.

Publications

• Type: Journal Articles Status: Published Year Published: 2016 Citation: Guo, L., and H.S. Lin 2016. Critical Zone research and observatories: Current status and future perspectives. Vadose Zone J. doi:10.2136/vzj2015.
• Type: Journal Articles Status: Published Year Published: 2016 Citation: Hopkins, I., H. E. Gall, and H.S. Lin. 2016. Natural and anthropogenic controls on the frequency of preferential flow occurrence in a wastewater spray irrigation field. Agricultural Water Management 178:248257.
• Type: Journal Articles Status: Published Year Published: 2016 Citation: Brantley, S.L., R. DiBiase, T. Russo, Y. Shi, H.S. Lin, K. J. Davis, M. Kaye, L. Hill, J. Kaye, A. L. Neal, D. Eissenstat, B. Hoagland, A. Dere. 2016. Designing a suite of measurements to understand the critical zone. Earth Surface Dynamics 4:211235. doi:10.5194/esurf-4-211-2016.