Mixing Model Approaches to Estimate Storm Flow Sources in an Overland Flow‐Dominated Tropical Rain Forest Catchment

Abstract

Mixing model approaches to estimate storm fl ow sources in an overland fl ow-dominated tropical rain forest catchment Abstract. Previous hydrometric studies demonstrated the prevalence of overland flow as a hydrological pathway in the tropical rain forest catchment of South Creek, northeast Queensland. The purpose of this study was to consider this information in a mixing analysis with the aim of identifying sources of, and of estimating their contribution to, storm flow during two events in February 1993. K and acid-neutralizing capacity (ANC) were used as tracers because they provided the best separation of the potential sources, saturation overland flow, soil water from depths of 0.3, 0.6, and 1.2 m, and hillslope groundwater in a two-dimensional mixing plot. It was necessary to distinguish between saturation overland flow, generated at the soil surface and following unchanneled pathways, and overland flow in incised pathways. This latter type of overland flow was a mixture of saturation overland flow (event water) with high concentrations of K and a low ANC, soil water (preevent water) with low concentrations of K and a low ANC, and groundwater (preevent water) with low concentrations of K and a high ANC. The same sources explained the streamwater chemistry during the two events with strongly differing rainfall and antecedent moisture conditions. The contribution of saturation overland flow dominated the storm flow during the first, high-intensity, 178-mm event, while the contribution of soil water reached 50% during peak flow of the second, low-intensity, 44-mm event 5 days later. This latter result is remarkably similar to soil water contributions to storm flow in mountainous forested catchments of the southeastern United States. In terms of event and preevent water the storm flow hydrograph of the high-intensity event is dominated by event water and that of the low-intensity event by preevent water. This study highlights the problems of applying mixing analyses to overland flow-dominated catchments and soil environments with a poorly developed vertical chemical zonation and emphasizes the need for independent hydrometric information for a complete characterization of watershed hydrology and chemistry. U n i v e r s i t ä t P o t s d a m

Stable-isotope and solute-chemistry approaches to flow characterization in a forested tropical watershed, Luquillo Mountains, Puerto Rico

“…In contrast to many previous studies, storm flow did not mix with or displace previously stored water (Bonell et al, 1998). Similar flow mechanisms have also been observed in other tropical catchment studies (Elsenbeer et al, 1995;Schellekens et al, 2004;Goller et al, 2005;Bonell, 2005;Kurtz et al, 2011), and in a temperate forest on granitic bedrock (Burns et al, 2001).…”

A three-component hydrograph separation based on geochemical tracers in a tropical mountainous headwater catchment in northern Thailand

“…Sharp rises of K + with the onset of fast-flow components were reported from tropical (e.g. Elsenbeer et al, 1995;Kinner and Stallard, 2004;Mul et al, 2008) and temperate study sites . Within the present study, a similar pattern was monitored during E2.…”

Organic carbon efflux from a deciduous forest catchment in Korea

“…Hence, it has long been recognized that one can only infer the movement and mixing of water from the natural tracer elements that the water carries (e.g., Pinder and Jones, 1969). Using various tracers, the end-member mixing analysis has been used to elucidate flow paths and hydrological processes in several catchments (e.g., Hooper et al, 1990;Elsenbeer et al, 1995;Katsuyama et al, 2001). Numerous conceptual models have adopted the flow path dynamics proposed by Anderson et al (1997), i.e., both pre-event soil water and bedrock groundwater contribute to the formation of a saturated zone in the area adjacent to the stream (e.g., McGlynn et al, 1999;Bowden et al, 2001;Uchida et al, 2002).…”