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ARS Home » Northeast Area » University Park, Pennsylvania » Pasture Systems & Watershed Management Research » Research » Publications at this Location » Publication #310844
Title: Long-term trends in climate and hydrology in an agricultural, headwater watershed of central Pennsylvania, USA

Author
item LU, HAIMING - Nanjing Research Institute For Agriculture
item Bryant, Ray
item Buda, Anthony
item Collick, Amy
item Folmar, Gordon
item Kleinman, Peter

Submitted to: Journal of Hydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/6/2015
Publication Date: 10/15/2015
Citation: Lu, H., Bryant, R.B., Buda, A.R., Collick, A.S., Folmar, G.J., Kleinman, P.J. 2015. Long-term trends in climate and hydrology in an agricultural, headwater watershed of central Pennsylvania, USA. Journal of Hydrology. 4(B):713-731. doi: 10.1016/j.ejrh.2015.10.004.

Interpretive Summary: Strategies to mitigate agricultural runoff must consider long-term changes in climate. We investigated temperature, precipitation and runoff trends over roughly four decades of monitoring an agricultural watershed in east central Pennsylvania (1968-2012). Temperature data confirmed a significant warming trend with longer growing seasons and shorter, milder cold seasons. The length of hydrological droughts during summer periods is increasing at a rate of 1.9 days per decade. Stream flow declined significantly in July and February, but increased in October, suggesting greater concern for nutrient loss in runoff during the fall. An observed decline in the number of snow-melt runoff events coincides with milder winters. While our findings do suggest some challenges for producers and water resource managers, some changes such as longer growing season can be viewed in positive light, and the implications for regional water quality protection are far from conclusive.

Technical Abstract: Strategies to mitigate agricultural runoff must consider long-term changes in climate. We investigated temperature, precipitation and runoff trends over roughly four decades of monitoring an agricultural watershed in east central Pennsylvania (1968-2012). Temperature data confirmed significant expansion of warm (mean daily temp > 0') and growing seasons, coinciding with a shortening of cold seasons (mean daily temp < -5'). No significant change in annual precipitation was observed. However, a significant increase in trace precipitation (< 2.5 mm/d) and a significant decrease in light precipitation (2.5-12.7 mm/d) were detected. Summertime periods of hydrological drought (maximum consecutive days with streamflow < 10th percentile) increased 1.9 days per decade. Stream flow declined significantly in July and February, but increased in October, suggesting greater concern with runoff during the fall. Milder winters (January mean minimum temperatures increased an average of 0.89') coincided with a decline in snow-melt events, from seven in the 1970s to five in the 1980s to one in subsequent decades. However, rainfall driven flooding was more variable, with nine in the 1970s, six, eight, and seven per decade in the 1980s, 1990s and 2000s, then five in 2010-2011. Annual evapotranspiration increased significantly (37.07 mm per decade), suggesting greater recharge of deep aquifers during the winter in association with shorter periods of snow cover and frozen ground. While our findings do suggest some challenges for producers and water resource managers, some changes can be viewed in positive light and the implications to regional water quality protection are far from conclusive.