Effects of Land Use on Flow Rate Change Indices

Abstract

Abstract:The goal of this study was to analyze the impact of agriculture on the spatial and temporal variability of flow rate change indices from 1930 to 2008. The two indices used are the coefficient of immoderation (CI) and the coefficient of variation (CV). Values of these two indices are higher for the L'Assomption River agricultural watershed than for the Matawin River forested watershed due to higher runoff in the former than in the latter. The difference in these values between the two watersheds is greater for winter, but it is lower for summer, when the difference in runoff between the two watersheds is strongly attenuated by the presence of crops. Regarding the temporal variability, a difference between the two watersheds is observed in the fall. For the agricultural watershed, mean values of neither index show a break in slope, while a break is observed for the forested watershed. In both watersheds, both indices are positively correlated with maximum temperature and total rainfall in winter, but only to this latter climate variable in the fall. In springtime, the two indices are negatively correlated with minimum temperature in the forested watershed, but only CV is correlated, positively, with this same climate variable in the agricultural watershed.

Comparison of Seasonal Flow Rate Change Indices Downstream of Three Types of Dams in Southern Quebec (Canada)

“…However, in natural rivers, both ecologically and geomorphologically speaking, this characteristic significantly influences the functioning and evolution of river ecosystems, just as much as the other four characteristics. As has already been mentioned by Assani et al [3], macrophytes and riparian vegetation are influenced by flow rate change. It is same with habitat volumes and the availability of food for aquatic and semi-aquatic fauna.…”

“…To fully characterize seasonal flow rate change with respect to hydrological variables, two indices suggested by Assani et al [3] were used. The first index is the coefficient of variation (CV), which is the ratio of standard deviation to the mean calculated over a daily flow series.…”

Analysis of the Influence of the 2007–2008 La Niña Events, Land Use, and Dam Management Modes on the 2008 Spring Freshet Characteristics in Quebec, Canada

“…• Spring freshet flow variability, measured using two indices [12]: the coefficient of variation (CV), expressed as a percentage, and the coefficient of immoderation (CI). The former index is a measure of the inter-day variability of flows during the freshet and the latter, which is the ratio of maximum (Qmax) and minimum (Qmin) flows during the freshet, is a measure of the maximum amplitude of the variability of extreme flows during the freshet.…”

“…As far as human factors are concerned, many dams have been built in Quebec since the nineteenth century to develop natural resources and fulfill the demand for both domestic and industrial hydroelectric power [4]. Many studies have looked at the impacts of these works on streamflow [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] and have shown that the extent of changes in streamflow downstream from these dams depends, among other things, on the dam management mode. Four management modes have been identified and described, each corresponding with a specific regulated hydrological regime downstream from dams.…”