A century of precipitation trends in forest lands of the Lower Mississippi River Alluvial Valley

Authors: OUYANG, YING - Forest Service (FS); ZHANG, JIAEN - South China Agricultural University; Feng, Gary; WAN, YONGSHAN - Environmental Protection Agency (EPA); LEININGER, THEODOR - Forest Service (FS)

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/2020
Publication Date: 7/30/2020
Citation: Ouyang, Y., Zhang, J., Feng, G.G., Wan, Y., Leininger, T.D. 2020. A century of precipitation trends in forest lands of the Lower Mississippi River Alluvial Valley. Scientific Reports. 10:12802. https://doi.org/10.1038/s41598-020-69508-8.
DOI: https://doi.org/10.1038/s41598-020-69508-8

Interpretive Summary: Variations in long-term precipitation trend due to climate forcings have been observed in many parts of the world. Such variations could exacerbate hydrological processes and add uncertainties to droughts, floods, water resources, and ecosystem services. Lower Mississippi River Alluvial Valley (LMRAV) is an economic artery in midsouth USA, which is prone to natural disasters from extreme climatic events and is well known for cyclic flooding events, groundwater level decline, and surface water quality degradation. However, our knowledge on long-term precipitation trends and their potetnial adverse impacts in this region is fragmented. Using 100 plus years precipitation data from four less disturbed forest lands of the LMRAV in conjunction with Mann Kendall’s analysis, we found that there were statistically significant (p < 0.05) increasing trends in monthly and annual precipitations as well as in number of annual mean wet days at decadal scale near the coastal area of the LMRAV over the past 100 plus years. A solid evidence was obsered that very profound (Kendall’s t = 0.6) and significant (p = 0.01) increasing trends in total amounts of precipitation during fall season at decadal scale near the coastal area of the LMRAV. Based on Log-Pearson type III analysis, we learned that the extreme precipitation intensity was larger with a shorter recurrence interval and a higher recurrence probability for the coastal area than for the inland area of the LMRAV. Results indicated that the coastal area of the LMRAV has become wetter with seasonality and was more vulnerable to climate change in terms of precipitation over the past 100 plus years. A large portion of crop lands in the LMRAV relies on irrigation with groundwater resources for enhancing grain yields. Therefore, our findings from this study are crucial to water resources management and irrigation strategy development in the region.

Technical Abstract: Variations in long-term precipitation trends due to climate forcings have been observed in many parts of the world, exacerbating hydrological uncertainties to predicting droughts, floods, water resource availability, and ecosystem services. The Lower Mississippi River Alluvial Valley (LMRAV) is an important economic region of the midsouth USA, which is prone to natural disasters from extreme climate events and is known historically for cyclic flooding events and, within the last 20 years, for groundwater level declines. However, our knowledge of long-term precipitation trends in this region is fragmented. Using 100-year historic daily precipitation data from six stations of forest lands along with multivariate statistical analysis, we found that there were significant increasing trends (p = 0.05)in annual precipitation near the south coastal area of the LMRAV and only marginally increasing trends in the northern area. Spatial variation in seasonality was observed at the decadal scale with increasing trends in fall near the coastal area and in spring around the north area. In addition to becoming wetter, the coastal area also experienced higher precipitation intensity with shorter return period over the past 100 years. These findings are useful to water resource managers for adapting to changing climate conditions in the LMRAV.