Abstract
Abstract. A set of complex processes contribute to generate river runoff, which in the hydrological sciences are typically divided into two major categories: surface runoff, sometimes called Hortonian flow, and baseflow-driven runoff or Dunne flow. In this study, we examine the covariance of global satellite-based surface water inundation (SWI) observations with two remotely sensed hydrological variables, precipitation, and terrestrial water storage, to better understand how apparent runoff generation responds to these two dominant forcing mechanisms in different regions of the world. Terrestrial water storage observations come from NASA’s Gravity Recovery and Climate Experiment (GRACE) mission, while precipitation comes from the Global Precipitation Climatology Project (GPCP) combined product, and surface inundation levels from the NASA Surface WAter Microwave Product Series (SWAMPS) product. We evaluate the statistical relationship between surface water inundation, total water storage anomalies (TWS; TWSAs), and precipitation values under different time lag and quality control adjustments between the data products. We find that the global estimation of surface inundation improves when considering a quality control threshold of 50 % reliability for the SWAMPS data and after applying time lags ranging from 1 to 5 months. Precipitation and total water storage equally control the majority of surface inundation developments across the globe. The model tends to underestimate and overestimate at locations with high interannual variability and with low inundation measurements, respectively.
Highlights
There is a long history of research concerning the mechanisms that control runoff generation at the terrestrial land surface (e.g., Beven and Kirkby, 1976; Pearce et al, 1986; Lyon et al, 2006; Vivoni et al, 2007; Kirchner, 2009)
It is generally well accepted that two major mechanisms are responsible for surface water formation: (1) excess precipitation and the limitation of infiltration causing surface runoff or (2) the rising of the water table and deeper soil moisture to push more water into stream networks at a low topography
We provided five correlation maps with different inputs: the model with Surface WAter Microwave Product Series (SWAMPS) and Gravity Recovery and Climate Experiment (GRACE) without a time lag correction (Fig. 10a), the model with SWAMPS and Global Precipitation Climatology Project (GPCP) without a time lag correction (Fig. 10b), the model with SWAMPS, GRACE, and GPCP without a time lag correction (Figs. 10c and 11a), and the model with SWAMPS, GRACE, and GPCP with a time lag correction of 0 to 5 months (Fig. 11b)
Summary
There is a long history of research concerning the mechanisms that control runoff generation at the terrestrial land surface (e.g., Beven and Kirkby, 1976; Pearce et al, 1986; Lyon et al, 2006; Vivoni et al, 2007; Kirchner, 2009). If precipitation rates exceed infiltration rates, precipitation dominates surface inundation development and is typically defined as Hortonian flow. If precipitation successfully infiltrates and soils become saturated, subsurface soil water storage will dominate surface water formation, typically described as Dunne flow. These are core concepts within terrestrial hydrology; there are limited observational studies on these runoff generation mechanisms at scales larger than a catchment. Using existing data on global precipitation and water storage and considering how these two mechanisms influence surface inundation development, it is possible to examine surface runoff mechanisms across a range of land surface conditions
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