Spatial Recognition of Regional Maximum Floods in Ungauged Watersheds and Investigations of the Influence of Rainfall

This study primarily aims to develop a method for estimating the range of flood sizes in small and medium ungauged watersheds in local river streams. In practice, several water control projects have insufficient streamflow information. To compensate for the lack of data, the streamflow propagation method (SPM) provides streamflow information for ungauged watersheds. The ranges of flood sizes for ungauged watersheds were generated using a specific flood distribution analysis based on the obtained streamflow data. Furthermore, the influence of rainfall information was analyzed to characterize the patterns of specific flood distributions. Rainfall location, intensity, and duration highly affected the shape of the specific flood distribution. Concentrated rainfall locations affected the patterns of the maximum specific flood distribution. The shape and size of the minimum specific flood distribution were dependent on the rainfall intensity and duration. The Creager envelope curve was used to generate equations for the maximum/minimum specific flood distribution for the study site. The ranges of the specific flood distributions were produced for each watershed size.

A novel method for cold-region streamflow hydrograph separation using GRACE satellite observations

Streamflow hydrograph analysis has long been used for separating streamflow into baseflow and surface runoff components, providing critical information for studies in hydrology, climate and water resources. Issues with established methods include the lack of physics and arbitrary choice of separation parameters, problems in identifying snowmelt runoff, and limitations on watershed size and hydrogeological conditions. In this study, a Gravity Recovery and Climate Experiment (GRACE)-based model was developed to address these weaknesses and improve hydrograph separation. The model is physically based and requires no arbitrary choice of parameters. The new model was compared with six hydrograph separation methods provided with the U.S. Geological Survey Groundwater Toolbox. The results demonstrated improved estimates by the new model particularly in filtering out the bias of snowmelt runoff in baseflow estimate. This new model is specifically suitable for applications over large watersheds which is complementary to the traditional methods that are limited by watershed size. The output from the model also includes estimates for watershed hydraulic conductivity and drainable water storage, which are useful parameters in evaluating aquifer properties, calibrating and validating hydrological and climate models, and assessing regional water resources.

Superlinear scaling of riverine biogeochemical function with watershed size

River networks are a crucial component of the earth system because they regulate carbon and nutrient exchange between continents, the atmosphere, and oceans. Quantifying the role of river networks at broad spatial scales must accommodate spatial heterogeneity, discharge variability, and upstream-downstream connectivity. Allometric scaling relationships of cumulative biogeochemical function with watershed size integrate these factors, providing an approach for understanding the role of fluvial networks in the earth system. Here we demonstrate that allometric scaling relationships of cumulative river network function are linear (power exponent ~ 1) when biogeochemical reactivity is high and river discharges are low, but become increasingly superlinear (power exponent > 1) as reactivity declines or discharge increases. Superlinear scaling indicates that biogeochemical function of entire river networks within a watershed is an emergent property that increases disproportionately with increasing watershed size. Expanding observation networks will increase precision in riverine fluxes of carbon and nutrients estimated by allometric scaling functions.

A novel method for cold region streamflow hydrograph separation using GRACE satellite observations

Streamflow hydrograph analysis has long been used for separating streamflow into baseflow and surface-runoff components, providing critical information for studies in hydrology, climate and water resources. Defects known with established methods include the lack of physics and arbitrary choice of separation parameters, problems in identifying snowmelt runoff, and limitations on watershed size and hydrogeological conditions. In this study, a GRACE-based model was developed to address these weaknesses and improve hydrograph separation. The model is physically based and does not require a priori parametrisation. The new model was compared with six hydrograph separation methods provided with the U.S. Geological Survey Groundwater Toolbox. The results demonstrated robust estimate by the new model particularly in filtering out the bias of snowmelt runoff in baseflow estimate. This new model is specifically suitable for applications over large watersheds which is complementary to the traditional methods that are limited by watershed size. The output from the model also includes estimates for watershed hydraulic conductivity and drainable water storage, which are useful parameters in evaluating aquifer properties, calibrating and validating hydrological and climate models, and assessing regional water resources.