Temporal inequality in catchment discharge and solute export

Abstract

[1] A framework is developed for characterizing the temporal inequality of stream discharge and solute loads to receiving waters using Lorenz diagrams and the associated Gini coefficient, G. These descriptors are used to illustrate a broad range of observed flow variability with a synthesis of multidecadal flow data from 22 rivers in Florida. Multidecadal phosphorus load data from four of the primary tributaries to Lake Okeechobee, Florida, and sodium and nitrate load data from nine of the Hubbard Brook, New Hampshire, long-term study site catchments are used to examine the relation between the inequality of flow and load. The intra-annual loads to Lake Okeechobee are shown to be highly unequal, such that 90% of the annual load is delivered in as little as 15% of the time. Analytic expressions are developed for measures of inequality in terms of parameters of the lognormal distribution under general conditions that include periods of zero flow. In cases where variability of concentrations is low compared to that of flows (chemostatic conditions), such as for phosphorus in the Lake Okeechobee basin and sodium in Hubbard Brook, the temporal inequality of flow is a strong surrogate for load inequality. However, in cases where variability of concentrations is high compared to that of flows (chemodynamic conditions), such as for nitrate in the Hubbard Brook catchments, load inequality is greater than flow inequality. The measured degree of correspondence between flow and load inequality for these data sets is shown to be well described using the general inequality framework introduced here.

Temperature and precipitation changes over the Loess Plateau between 1961 and 2011, based on high-density gauge observations

“…Recently, the concept has been applied to other research fields, such as inequalities in global water use (Seekell et al, 2011) and plant size and fecundity (Damgaard and Weiner, 2000), and temporal inequalities in catchment discharge (Jawitz and Mitchell, 2011;Masaki et al, 2014). Rajah et al (2014) used the Gini coefficient to analyze the distribution of precipitation and changes in precipitation.…”

Subsurface release and transport of dissolved carbon in a discontinuous permafrost region

“…Recent work by Jawitz and Mitchell (2011) has demonstrated that considering the ratio of the variances of log-transformed loads and log-transformed flows may provide improved understanding of the interplay between concentrations and loads in relation to chemostasis. By adopting such an approach, analytical solutions for the solute export equations describing the correlation between mass fluxes and discharge (such as that seen in Fig.…”

Emergent archetype patterns of coupled hydrologic and biogeochemical responses in catchments

“…A constant pattern exhibits little directional changes in C with changes in Q (b~0), as observed for Ca 2+ and other ions with geogenic sources [Godsey et al, 2009;Thompson et al, 2011]. We define chemostatic and chemodynamic solute export regimes (Figures 1b and 1c and S1), based on the relative temporal variability in C compared to Q [Jawitz and Mitchell, 2011;Thompson et al, 2011]. We define chemostatic and chemodynamic solute export regimes (Figures 1b and 1c and S1), based on the relative temporal variability in C compared to Q [Jawitz and Mitchell, 2011;Thompson et al, 2011].…”

“…Note that these authors have referred to b~0 as "chemostatic," but we prefer "constant" because we reserve the former term for export regimes, which we define below as differentiated from C-Q patterns. Chemostatic export regimes have been observed for geologic weathering products such as Ca +2 , Mg 2+ , and K + [Godsey et al, 2009;Herndon et al, 2015;Musolff et al, 2015], as well as anthropogenically mediated solutes, such as NO 3 À and PO 4 À [Basu et al, 2010;Jawitz and Mitchell, 2011], and animalborne hormones [Gall et al, 2016]. In chemostatic export regimes, the coefficient of variation (CV) is low for C relative to Q, with CV C /CV Q ≤ 0.5 independent of slope b. Consequently, exported solute load variance CV L is dominated by discharge variance which reflects in CV L /CV Q~1 .…”