Abstract

While prolonged drought has long challenged water managers and planners in the western US, recent droughts in the southeast US, such as the 2007-2009 drought that impacted Lake Lanier and water supply in Georgia (Atlanta), have resulted in the need to address drought in the southeast United States. While the southeast experiences much greater precipitation amounts than most of the western US, the increased population and agricultural demands have stressed water resources. The southeast US is also unique in that from June thru November, there is a probability of tropical cyclones (hurricanes, tropical depressions, etc.). These events can produce extreme amounts of precipitation and, thus, lead to flood events. Drought and flood events impact stakeholders, commerce and can result in the loss of property and human life. There is a need to evaluate the present, future and past of these extreme events in the southeast US, in particular coastal regions of Mississippi (MS) and Alabama (AL).

The proposed research will evaluate MS/AL coastal streamflow in the present (observed records including the impact of climate signals), in the future (using high resolution hydrologic models and future predictions of climate), and in the past (paleo records using tree-ring datasets). The proposed research will result in flood / drought hazard planning in all five coastal counties and will generate a minimum of three peer-reviewed publications in high impact journals.

Objectives

Objective A: To determine climate signals (e.g., El Nino-Southern Oscillation – ENSO, etc.) in observed streamflow records and their impact on MS/AL coastal hydrology and what predictive signal these climate signals may provide.

Objective B: To utilize future predictions of climate (precipitation, temperature, wind) in hydrologic models to determine future streamflow extremes.

Objective C: To generate paleo reconstructions of streamflow using tree-ring datasets and assess drought and wet/flood periods, including the frequency, severity, magnitude and duration of these events, comparing these paleo records to observed and future streamflows.

Objective D: To engage local decision makers (and stakeholders) in evaluating and assisting in planning for future extreme (drought, flood) events.

Methodology

Objective A: Parametric (e.g., t-test) and non-parametric (e.g., rank-sum test) testing of climate signals (e.g., El Nino, etc.) and streamflow response to determine, with significance, if a climatic driver (teleconnection) can be established. Singular Value Decomposition will be used with spatial (gridded) sea surface temperatures (SSTs) and streamflow to identify a specific region of SSTs that teleconnect with streamflow. The climatic drivers identified will be used in a non-parametric model to forecast streamflow.

Objective B: The Community Earth System Model (CESM), Coupled Model Intercomparison Project Phase 5 (CMIP5) scenario forcings (precipitation, temperature, etc.) for 1/24 degree (4 km) resolution for future (2015 to 2100) periods will be used in the Variable Infiltration Capacity (VIC) model for watersheds that contribute to the five target coastal counties.

Objective C: Streamflow data from the USGS and tree-ring data from the NOAA-NCDC International Tree Ring Database will be used in regression (stepwise, partial least squares) models to develop paleo reconstructions of streamflow. Drought and flood frequency analysis (Weibull, Compound Renewal and Drought Risk using bivariate probability distribution functions) will be performed on paleo streamflow and compared to observed (instrumental) and future streamflow.

Objective D: Workshops, town halls and peer-reviewed publications will disseminate the research results to interested parties.

Rationale

Objective A: Long (3 to 9 months) lead-time forecast models for streamflow will provide local decision makers and stakeholders a decision tool for water supply that can be used in future planning. Per the RFP: Residents and decision-makers are aware of and understand the processes that produce hazards….and the implications of those processes for them and their communities.

Objective B: Future projections of streamflow including extreme (dry/drought and wet/flood) events will be identified. Thus, a decision tool for water planners and managers in drought/flood preparation and mitigation will be developed. Per the RFP: Residents and decision-makers are aware of and understand the processes……including climate change and the implications of those processes for them and their communities.

Objective C: Paleo streamflow reconstructions will provide an historic basis for past drought/flood events and for comparison to observed and future events. The frequency analysis of extreme events in paleo, observed and future streamflow will provide a decision tool for water managers and planners. Per the RFP: Communities have access to data and innovative and adaptive tools and techniques to minimize the potential negative impact from hazards.

Objective D: The decision tools (Long lead-time forecasts using climate signals; future extreme events; past extreme events; quantification of these extreme events) will be disseminated to decision makers, stakeholders and to the research community via peer-reviewed journal publications. Per the RFP: Communities use comprehensive planning to make informed strategic decisions. Communities apply best available hazards and climate change information, and tools and technologies in the planning process.