Location: Sustainable Water Management Research
Project Number: 6066-13000-006-043-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Jul 1, 2026
End Date: Jun 30, 2028
Objective:
The overall objective of this agreement is to increase producer profitability while also ensuring the long-term health of the soil and natural resources needed for agriculture, in keeping with the Secretary's research priorities. Irrigation from groundwater sources is the most common way for producers in the Mississippi Delta to mitigate risk and ensure viable crop production. Unlike most other agricultural production areas, the Mississippi Delta uses irrigation to supplement precipitation not as a complete replacement. Developing a reference evapotranspiration (ET) network will allow an accurate understanding and estimation of crop water usage due to both plant transpiration and atmospheric evaporation.
This project is divided into four objectives.
Objective 1: Evaluation of all publicly available weather stations, within the study area, for data quality.
Objective 2a: Computation of daily reference ET (ETo) at all quality-controlled stations using the standardized reference ET equation of the American Society of Civil Engineers - Environmental and Water Resources Institute (ASCE-EWRI).
Objective 2b: Conduct sensitivity analysis of weather variables to reference ET.
Objective 3: Identification of potential locations for establishing reference ET stations.
Objective 4: Analysis of long-term spatial and temporal trends in frost and other weather-related indices.
Approach:
An orderly plan has been developed to achieve the objectives of this project.
The first objective is to conduct a comprehensive inventory and systematic quality control (QC) assessment of all meteorological stations operating across the Mississippi Delta region. Existing stations from multiple independent networks including the Mississippi Agricultural Weather Network (MAWN), the Arkansas Mesonet, the National Oceanic and Atmospheric Administration’s Automated Surface Observing System (ASOS), the Cooperative Observer Program (COOP), the USDA Soil Climate Analysis Network (SCAN), and the Global Historical Climatology Network-Daily (GHCN-D) will be compiled into a unified station registry with full metadata documentation covering sensor types, measurement heights, known relocation events, and period of record. Each station will then undergo a four-stage QC protocol: physical range and limit checks to flag implausible values; internal consistency checks to identify logical conflicts such as maximum temperatures falling below minimum temperatures or relative humidity exceeding 100%; spatial regression quality control, in which observed values are compared against predictions from neighboring stations to isolate outliers. Missing records will be reconstructed through linear regression imputation for short gaps and Multiple Imputation by Chained Equations for extended gaps. The final product will be a curated, quality-tiered, gap-filled daily weather dataset covering 1960–2024, suitable for all downstream analyses in the project.
The second objective will compute daily reference evapotranspiration (ET), also known as ETo, at all quality-controlled stations and perform a systematic sensitivity analysis to quantify the relative influence of each driving weather variable on reference ET estimates. A local one-at-a-time (OAT) approach will be employed, where each input variable (maximum and minimum air temperature, relative humidity, wind speed at two meters, and solar radiation) is perturbed by ±5%, ±10%, and ±20% of its observed mean while all remaining inputs are held constant. This enables the derivation of a normalized sensitivity coefficient for each variable at every station and for each month of the year, providing a rigorous, station-specific characterization of how errors or uncertainties in individual meteorological measurements propagate into reference ET estimates.
For the third objective, a time series of spatially interpolated ETo maps across the Mississippi Delta to quantify the spatial variability and long-term trends in reference ET, and to identify optimal locations for the establishment of future ETo monitoring stations will be developed.
The fourth objective is to characterize how frost indices have evolved across the Mississippi Delta over the past six decades and to elucidate the spatial patterns and underlying drivers of those changes. Frost index dynamics carry important implications for defining growing season boundaries for major crops, estimating crop water demand, and informing adaptation strategies that extend beyond irrigation management alone.