Knowledge Resource Center for Ecological Environment in Arid Area
| 项目编号 | 1019348 |
| From Mountains to Deserts: Using Watershed Science to Study the Impacts of Global Change on California鈥檚 Natural Resources | |
| Sickman, J | |
| 主持机构 | SAES - UNIVERSITY OF CALIFORNIA AT RIVERSIDE |
| 开始日期 | 2019 |
| 结束日期 | 2023 |
| 资助机构 | US-NIFA（美国食品与农业研究所） |
| 语种 | 英语 |
| 国家 | 美国 |
| 中文简介 | 1190 - Limnology |
| 英文简介 | Goals / Objectives The recent Millennial Drought in California (Griffin and Anchukaitis, 2014) and the ongoing multidecadal drought in the Rocky Mountains (Castle et al., 2014) highlight the vulnerability of our modern society to water availability and climate variability (Famiglietti, 2014). The Central Valley, Coachella Valley and Imperial Valley are the nexus for agricultural activity and water supply in California. Most of the irrigated agriculture in these regions of California are supplied by snowmelt from the Sierra Nevada, Colorado River flow or groundwater pumping. For example, snowmelt runoff from the Sierra Nevada provides municipal and agricultural water for over 25-million Californians and is a main driver of economic prosperity in the State. With climate changing in response to anthropogenic emissions of greenhouse gases, water scarcity is expected to intensify with reductions in western US precipitation, shifts from mountain snow to rain, and greater water demands by society brought on by increasing urbanization and higher temperatures (AghaKouchak et al., 2015).In California, landuse change has been occurring for more than 100 years and has led to large-scale conversion of natural and agricultural lands to cities. Seven of the 10 most densely urbanized regions of the United States are found in California, with the Los Angeles metro area having the highest population density in the US of about 7,000 people per square mile (World Population Review 2019). These patterns of landuse change are interacting with climate change to create additional stressors for natural and agricultural ecosystems including larger wildfires and altered atmospheric composition (greenhouse gases, NOx, SOx and aerosols). The environmental changes now occurring are unprecedented, interacting in complex ways and are resulting in degradation of agricultural productivity, human health, ecosystem services and water supply in California.Watershed science is a multidisciplinary method of studying the earth at local to regional scales using hydrologic connectivity as a unifying theme. Watershed science considers the exchange of energy, water and elements among the atmosphere, land and aquatic components of a defined land area that drains to a common sink (e.g., lake, reservoir, bay, estuary or similar receiving body). The study of watersheds usually involves the quantification of precipitation and runoff, atmospheric deposition and weathering and other earth surface processes that contribute to large-scale cycles of important elements (e.g., carbon cycle, nitrogen cycle etc.). Watershed science typically considers hydrologic and biogeochemical processes operating at intermediate spatial scales, 0.1 km2 to 106 km2, and usually integrates field and satellite measurements, often using these measurements in mechanistic models of surface and subsurface processes.My AES-Hatch project seeks to address important research questions regarding human impacts on terrestrial and aquatic ecosystems in California using the discipline of watershed science. I will focus on two important regions of California, both of which encompass critical areas for agriculture and natural resources: i) the southern Sierra Nevada-San Joaquin Valley mountain elevational continuum and ii) the southern California coastal to desert climatic continuum. In the Sierra Nevada, I have been involved in watershed and lake research for four decades and my current research program seeks to understand the responses of montane ecosystems to global change drivers such as warming climate, changing snow regime and increased atmospheric deposition of acid and nutrients. In southern California I am studying the impacts of atmospheric deposition on nitrogen (N) cycling in dryland ecosystems including development of novel isotopic methods for measuring N deposition and for studying the biogeochemical processes involved in production of N gas emissions from soils.My research project is highly relevant to current UC ANR Strategic Initiatives including Sustainable Natural Ecosystems and Water Quality, Quantity and Security. Montane and desert ecosystems of California provide a broad range of ecosystem services including clean water, clean air, biodiversity, recreational activities and solitude. Two cross-cutting themes for these ANR Initiatives are water supply and climate change. My project addresses these themes in the context of California's water supply in several ways: i) I am addressing the interactive effects of climate change and altered atmospheric composition on terrestrial and aquatic ecosystem services, ii) I am using instrumental data as well as paleoclimate archives (lake sediments) to understand past variability of Sierra Nevada snowfall and help predict future trajectories for California's ecosystems and water supply, and iii) I am expanding the scale of my watershed studies in the southern Sierra Nevada to improve understanding of elevational contributions to mountain runoff which will contribute to the sustainable use of Sierra Nevada runoff in the southern San Joaquin Valley.My research will be conducted with a broad range of collaborators including AES faculty researchers at UCR, Faculty at UC Davis and UC Santa Barbara, Federal land management agencies such as the National Park Service and Bureau of Land Management, the UC Natural Research system and through citizen-scientists living in the Kaweah River Watershed. The research outcomes of this project are expected to improve sustainability of ecosystem services derived from a broad suite of California's ecosystems (Sierra alpine through the Mojave Desert).Objectives The major objectives of my Hatch research in the Sierra Nevada-San Joaquin region are to:a. Continue my multidecadal watershed research program in the headwaters of the Kaweah River. This multidisciplinary investigation is focused on measurements of inputs and outputs of energy, water and elements (chiefly acids and nutrients) in the Marble Fork of the Kaweah River.b. Expand the spatial scale and scope of these watershed studies to study hydrogeochemistry in the lower elevation regions of the Kaweah River basin with the goal of understanding the sub basin and elevational contributions of runoff to river discharge.c. Use stable isotope measurements and modern fast-response gas analyzers, to quantify long-range transport, deposition and re-emission of air pollutants, principally oxidized and reduced forms of nitrogen, from the Los Angeles urban core through the Inland Empire and into the desert regions of the Coachella and Imperial Valleys.Project Methods 1. Watershed Research Program in the Marble Fork of the Kaweah RiverThe objective of this element of the project, is to improve understanding of the individual and interactive effects of climate change and atmospheric deposition on terrestrial and aquatic ecosystems in the Sierra Nevada.Our current weather and gauging stations will measure climate and hydrologic conditions every 10-seconds and record hourly averages on Campbell dataloggers. Parameters measured include short and long-wave radiation, wind speed and direction, temperature and relative humidity, soil moisture and temperature and two of the stations have cameras for determining snow covered area. The gauging stations are equipped with pressure transducers and staff gauges for stage measurements. Rating curves are derived from weirs (Emerald and Topaz) or by dye-dilution measurements of discharge at other locations. The gauging station at the western portion of the basin is equipped with a cable car for discharge measurements and water sampling during high flows.Liquid precipitation is quantified by tipping bucket rain gauges installed at two of the weather stations (Emerald and Topaz). Winter precipitation is measured as snowfall at maximum accumulation which occurs on or near April 1. To estimate snow water equivalence we perform an annual snow survey in April, where snow depths are measured at several hundred points and georeferenced with GPS; snow density is measured in snowpits using a steel snow tube (volume = 1 liter) and which is used to core the snow and the cores weighed on a calibrated balance. To quantify atmospheric deposition in the winter, snow samples are collected in a vertical profile from snowpits which integrates total atmospheric deposition from approximately November to April. To measure atmospheric deposition in non-winter periods we will use ion-exchange-resin (IER) collectors (Sickman et al., 2019). The IER collector is built of PVC and is designed similarly to a conventional throughfall collector except that the deposition is funneled through an ion exchange resin column where the anions and cations are reversibly adsorbed on a mixed-bed resin. In the laboratory the resins will be removed from the collector, stripped with an HCl solution and the eluate will be assayed for nutrients and major ions.Hydrologic fluxes from the Marble Fork and its subcatchments are determined as the product of discharge (measured at gauging stations) and solute concentrations. Solute concentrations in streams are measured in water samples collected periodically from Emerald, Topaz and the main stem of the Kaweah river; during the winter. Samples are also collected from Emerald Lake by auguring a hole in the ice and using a pump to collect water from multiple depths. During snowmelt, stream samples are collected by automated samplers and during other periods by field personnel.Water samples are split into filtered and unfiltered aliquots after collection and stored refrigerated in clean HDPE bottles. pH is measured on unfiltered samples using a pH meter and electrode designed for dilute waters. ANC is determined by Gran titration using 0.1 N HCl. Conductivity is measure with a conductivity meter and electrode. Anions (Cl-, NO3- and SO42-) are measured by ion chromatography. Cations (Ca2+, Mg2+, Na+ and K+) are measured by ICP-OES. Ammonium is measured colorimetrically on a Seal AQ2 discrete analyzer.2. Sub Basin and Elevational Contributions to Runoff from the Kaweah River WatershedThis project will:a. Quantify the contributions of each major fork of the Kaweah River to the main stem of the Kaweah River above Terminus Dam.b. Quantify the relative elevational contributions of runoff within each Kaweah River sub basin and to the main stem of the Kaweah River.The project will use the existing hydrologic monitoring infrastructure in the Kaweah River basin including: i) the previously described subalpine - alpine watershed observatory in the Marble Fork of the Kaweah, ii) the Wolverton Creek catchment observatory in the Kaweah mixed conifer zone operated by UC Merced, iii) snow courses and snow pillow measurements made by the California Department of Water Resources, and iv)climate and gauging stations in other reaches and forks of the Kaweah River basin operated by the National Park Service, US Geological Survey, Southern California Edison (an electrical utility) and the Army Corp of Engineers near Terminus dam.We will utilize both isotopic and chemical parameters to quantify contributions of water. Water samples of all hydrologic fluxes will be collected for analysis including: i) snowpack (alpine and subalpine zones), ii) rainfall (collected at existing National Atmospheric Deposition Program stations operated by the Park Service in the mixed conifer and foothill zones), iii) river flow from each major fork of the Kaweah River and the combined flow above Terminus Dam.Hydrogen and oxygen isotope composition of water (delta18O, delta17O and delta2H) will be measured on a Los Gatos Research (LGR) Liquid Water Isotope Analyzer at the Facility for Isotope Ratio Mass Spectrometry at UCR. Conservative (Na+ and Cl-) and semi-conservative elements (Ca2+, Mg2+, K+, and SO42-) will be measured using ion chromatography and ICP-OES at the Environmental Sciences Research Laboratory at UCR. Manuscripts will be prepared from this research and submitted to technical journals for publication.3. Transport, Deposition and Re-emission of Nitrogenous Air Pollutants in Southern CaliforniaI am collaborating with a team of UCR researchers to test this hypothesis. Our main objectives are to:a. Determine how N pulse emissions from soils vary spatially and temporally downwind of Los Angeles, andb. Determine the ultimate (anthropogenic, or soil) and proximate (biogenic or abiotic) sources of these pulsed soil N trace gas emissions.Our team consists of Dr. Darrel Jenerette (PI - UCR), Dr. Emma Aronson (UCR), Dr Jun Wang (University of Iowa) Dr. Peter Homyak (UCR), Dr. Mark Fenn (US Forest Service) and me. The project consists of: i) baseline monitoring of N deposition from Riverside eastward into the Mojave Desert, ii) measurement of N trace gas emissions during ambient conditions and during soil wetting and nutrient addition experiments using spectrometers and passive samplers (Bytnerowicz et al., 2005), iii) use of modern molecular methods to identify the biogenic contribution to soil N emissions at fine temporal resolutions and iv) use of a community atmospheric chemistry transport model, WRF-Chem, to simulate the deposition and re-emission of atmospheric N. Manuscripts will be prepared from these analyses and submitted to technical journals for publication.My principal contribution to the study is the planning and implementation of isotope tracers used during the soil wetting experiments and in measurements of atmospheric deposition. In the tracer experiments isotopically enriched nitrate and ammonium is added to the soils and the 15N tracer is incorporated into the emissions of NO, N2O and NH3. I am using passive samplers (Ogawa USA) to collect NO for isotope analysis. Nitric oxide collected on the filters is eluted with deionized water and its isotopic composition (delta15N and delta18O) is determined by isotope ratio mass spectrometry using the microbial denitrifier method (Coplen et al., 2012).Atmospheric deposition will be estimated using passive samplers that collect HNO3, NO and NH3. In Riverside we will also employ the integrated total nitrogen input method (ITNI) to measure total N deposition. The ITNI method uses the principle of isotope dilution to measure all forms of N deposition entering a plant-soil-water microcosm (Sickman et al., 2019). Once the microcosm is harvested and all components measured for N mass and delta15N, we can compute the total areal rate of N deposition. |
| 英文关键词 | sierra nevada mojave desert san joaquin valley watershed lakes atmospheric deposition climate change |
| 来源学科分类 | 1190 - Limnology |
| 资源类型 | 项目 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/356129 |
| 推荐引用方式 GB/T 7714 | Sickman, J.From Mountains to Deserts: Using Watershed Science to Study the Impacts of Global Change on California鈥檚 Natural Resources.2019. |
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