Water Quality

Working Group


As part of the LTAR Network, the Water Quality Working Group focus is to maintain or improve water quality and aquatic ecosystem services while maintaining and/or enhancing agricultural productivity. Long-term goals include: a) effective pollutant management; b) improved modeling; and c) balance between agricultural productivity and water quality leading to healthy watershed ecosystems.


  • Assess different aspects of water quality in agricultural landscapes across broad spatial and temporal scales.
  • Develop strategies that reduce the potential negative water quality impacts of increased agricultural productivity.
  • Enhance modeling efforts leading to more accurate assessment tools and more effective mitigation and conservation measures.
  • Long-term effective pollutant management, improved modeling, balance between agricultural productivity and water quality providing a functioning ecosystem.


  • Current Projects

    • Watershed Lag Time Project (WTLP): Takes advantage of a past change in the chemical formulation (chirality) of the widely used herbicide metolachlor that is reflected in its degradation product (known as MESA). Analysis of the chirality of MESA in rivers serves as a tracer of the time scale of watershed export of agrochemicals, thereby providing information that is valuable for understanding and mitigating agricultural contamination of surface waters.
    • in-Situ Water Quality Monitoring: Develop robust real time water quality monitoring strategies to better characterize and quantify contaminant sources and movement in agricultural watersheds across the LTAR watersheds.
    • Cross-Site Dissolved Organic Matter (DOM) Comparison: Examine differences and similarities in DOM chemical composition of surface waters across LTAR sites to understand the relationship between agricultural land use and DOM availability to microbes, an important ecological characteristic of surface waters.


    Future Projects

    • Watershed Nutrient Export in Relation to Streamflow Regimes: Compare the timing and magnitude of stream transport of nutrients (NO3 and dissolved reactive PO4-3) export from agricultural landscapes to better understand soruces and pathways of nutrient movement from land to water across LTAR watersheds.
    • Legacy Phosphorus and P Budgets: Assessing legacy phosphorus in soils and sediments (i.e., stored phosphorus accumulated from past land uses) and develop phosphorus budgets for agricultural systems to improve phosphorus management across LTAR watersheds.
    • Algal Nutrient Limitation and Thresholds: Provide information on which nutrients limit eutrophication and nutrient concentration thresholds that elicit algal blooms across LTAR watersheds to better understand nutrient mitigation needs.


  • Water Quality Data Survey conducted across various LTAR sites including type of water sampled, number of sites, contaminants measured, length of record, land-use and cropping systems.
  • Ongoing Water Quality Monitoring at 20 edge-of-field sites (two paired fields per site) measuring nutrient losses from surface and subsurface drainage from tile drained landscapes resulting in over 420 site years of data.
  • In-situ Measurements including ongoing common measurements using real-time water quality sensors for the LTAR network since 2016.
  • Cross-Site DOM Water Sample Analysis to reveal the variability in DOM quality of water samples collected from 13 LTAR stations.
  • Watershed Lag Time Project developed and validated a passive monitoring system to quantify the chirality of MESA as a tracer of watershed transport lag times. Over 1200 archived samples were analyzed by LC-MS/MS so that temporal changes can be examined. This project was highlighted by the NRCS Chief at a recent Water Sub-Cabinet meeting where legacy nutrients were discussed as part of an on-going interagency planning effort.

Datasets Produced

  • Runoff (concentrations and loads):
    • suspended sediment
    • dissolved organic carbon
    • nutrients: TN, TP, NO3-N, NO2-N, NH4-N, PO4-3
    • pesticides: herbicides, insecticides
  • Within-Channel Lake, River, Stream (concentrations):
    • suspended sediment
    • dissolved organic carbon
    • nutrients: TN, TP, NO3-N, NO2-N, NH4-N, PO4-3
    • pesticides: herbicides, insecticides
    • chlorophyll
  • In-Situ sensors:
    • turbidity
    • temperature
    • conductivity
    • pH
    • dissolved oxygen
    • NO3-N

Manuscripts Published

  • Pisani, O., Bosch, D.D., Coffin, A.W., Endale, D.M., Liebert, D., Strickland, T.C. 2020. Riparian land cover and hydrology influence stream dissolved organic matter composition in an agricultural watershed. Science of the Total Environment 717, 137165 DOI doi.org/10.1016/j.scitotenv.2020.137165.

  • Plummer, R.E., Hapeman, C.J., Rice, C.P., McCarty, G.W., Schmidt, W.F., Downey, P.M., Moorman, T.B., Douglas, E.A., Strickland, T.C., Pisani, O., Bosch, D.D., Elkin, K.R., Buda, A.R. 2020. Method to evaluate the age of groundwater inputs to surface waters by determining the chirality change of metolachlor ethanesulfonic acid (MESA) captured on a polar organic chemical integrative sampler (POCIS). Journal of Agricultural and Food Chemistry. 68(8):2297-2305. https://doi.org/10.1021/acs.jafc.9b06187.

  • Rice, C., Hively, W.D., McCarty, G.W., Hapeman, C.J. 2020. Fluxes of agricultural nitrogen and metolachlor metabolites are highly correlated in a first order stream in Maryland, USA. Science of the Total Environment. 716:136590. https://doi.org/10.1016/j.scitotenv.2020.136590.

Working Group Name

Water Quality Working Group


Richard Lizotte
Ray Bryant


Betsey Boughton – ABS
Stephen Hamilton – KBS
Claire Baffaut – CMRB
Bob Lerch – CMRB
Kevin Cole – UMRB
Tom Moorman – UMRB
Ray Bryant – UCB, co-leader
Kyle Elkin – UCB
Cathleen Hapeman – LCB
Greg McCarty – LCB
Cliff Rice – LCB
Kevin King – ECB
Rocky Smiley – ECB (biology liaison)
Mark Williams – ECB
Laura Johnson – ECB
Doug Smith – TGC
Richard Lizotte – LMRB, co-leader (communications liaison)
Martin Locke – LMRB (leadership liaison)
Darlene Wilcox – LMRB (data manager)
Jason Taylor – LMRB
Oliva Pisani – GACP



The USDA Agricultural Research Service (ARS) Long-Term Agroecosystem Research network consists of 18 Federal and university agricultural research sites with an average of over 50 years of history. The goal of this research network is to ensure sustained crop and livestock production and ecosystem services from agroecosystems, and to forecast and verify the effects of environmental trends, public policies, and emerging technologies.