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Abstract Harmful algal blooms (HABs) in aquatic ecosystems are of concern worldwide. This review deals with how jurisdictions around the world are addressing this water quality issue to inform recommendations regarding nutrient loading and HABs in Missisquoi Bay-Lake Champlain and Lake Memphremagog; transboundary lakes located in the USA and Canada that suffer from symptoms of eutrophication. A global scan of the literature resulted in the consideration of 12 case studies of large water bodies within large watersheds, excluding in-lake geoengineering approaches. Although all of the systems experience excessive nutrient loading, they vary in two key ways: sources of nutrients and manifestations of eutrophication ranging from HABs, to limited recreational uses, to the additional complexity of internal loadings and fish kills, up to drinking water shutdowns. The case studies were analyzed with respect to four categories of approaches, namely: (i) regulatory; (ii) incentive-based; (iii) risk mitigation; and (iv) outreach, engagement, and educational. We found that the management frameworks are based on integrated watershed management planning and national standards. National water quality standards, however, are not stringent enough to prevent HABs. Overall, identified case studies did not successfully remediate HABs, they simply managed them.

Located at the interface between terrestrial ecosystems and water resources such as water courses and shallow water tables, wetlands are a pivotal part of the drainage network of a watershed.Consequently, they affect the routing of overland and subsurface flows through modification of hydrological processes, namely increased evapotranspiration, water storage and groundwater recharge (Bullock and Acreman, 2003). These interactions have led researchers and land planners to attribute some hydrological services to wetlands, such as low flow support and high flow attenuation. As defined by Roche (1986), low flows refer to the lowest annual flow of a water course at a given point in space.To characterize low flows, various hydrological indicators have been defined, taking into account the return period: 2-year minimum flow over 7 days, 10-year minimum flow over 7 days, 5-year minimum flow over 30 days, etc. On the other hand, high flows are defined as the peak flow within a specific return period, typically 2-, 20-or 100-year maximum flows.In the last century, anthropic activities such as agricultural and urban development have induced major land cover changes; affecting the hydrological regime of watersheds (St-Hilaire et al., 2015;Salvadore et al., 2015;Savary et al., 2009;DeFries and Eshleman, 2004). Agricultural impacts on hydrological processes are mostly associated with artificial drainage, which alters the water volume and timing of runoff (e.g.: Muma et al., 2016;Blann et al., 2009). For example, in the Redwood basin, a Midwestern United States agricultural basin, the total area of soybean (associated with the installation of extensive subsurface drainage tiles) increased from 15% to 40% between 1971 and 2002, and this led to an increase in mean annual flows from 2.3 m 3 /s to 6.0 m 3 /s (Foufoula-Georgiou et al., 2015). Similarly, Muma et al. (2016) showed that subsurface drainage increased base and total flows, and decreased peak flows of an intensively farmed 2.4 km 2 watershed (90% in cropland with 30% of the watershed area tile-drained). As for the impacts of urban development on hydrology, characterized by increasing impervious surfaces, they range from affecting water supply by limiting infiltration, to changes in water demand in response to an increased population (DeFries and Eshleman, 2004;Diem et al., 2018). In the Atlanta metropolitan area, impervious cover of the Big Creek and Suwanee Creek watersheds increased from 8 to 17% and from 9 to 21% respectively, between 1992 and 2011, inducing an increase in the annual stream flow of 26% (Diem et al., 2018).Anthropic activities have also led to the draining of wetlands and modification of the land cover within their drainage area (Zedler and Kercher, 2005;Brinson and Malvarez, 2002). At the global scale, wetland losses estimations are up to 87% and the yearly rate of these losses accelerated between -0.68 to -0.69% in the 1970s to between -0.85 to -1.60% in the 2000s, depending on the region (Davidson, 2014; Ramsar Convention on Wetland, 2018). In all li...

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1Low flow conditions are governed by short-to-medium term weather conditions or long term 2 climate conditions. This prompts the question: given climate scenarios, is it possible to 3 assess future extreme low flow conditions from climate data indices (CDIs)? Or should we 4 rely on the conventional approach of using outputs of climate models as inputs to a 5 hydrological model? Several CDIs were computed using 42 climate scenarios over the years 6 1961 to 2100 for two watersheds located in Québec, Canada. The relationship between the 7 CDIs and hydrological data indices (HDIs; 7-and 30-day low flows for two hydrological 8 seasons) were examined through correlation analysis to identify the indices governing low 9 flows. Results of the Mann-Kendall test, with a modification for autocorrelated data, clearly 10 identified trends. A partial correlation analysis allowed attributing the observed trends in HDIs 11 to trends in specific CDIs. Furthermore, results showed that, even during the spatial 12 validation process, the methodological framework was able to assess trends in low flow 13 series from: (i) trends in the effective drought index (EDI) computed from rainfall plus 14 snowmelt minus PET amounts over ten to twelve months of the hydrological snow cover 15 season or (ii) the cumulative difference between rainfall and potential evapotranspiration over 16 five months of the snow free season. For 80% of the climate scenarios, trends in HDIs were 17 successfully attributed to trends in CDIs. Overall, this paper introduces an efficient 18 methodological framework to assess future trends in low flows given climate scenarios. The 19 outcome may prove useful to municipalities concerned with source water management under 20 changing climate conditions. 21 22 Keywords: 23 effective drought index; 7-day low flow; 30-day low flow; HYDROTEL; trends; climate model 24 for the 2001-2100 period, (ii) uncertainty of the climate change signal was addressed through 78 the use of 42 climate simulations, and (iii) future flows were simulated using a distributed 79 hydrological model. 80 Materials and methods 81The organization and mapping of the Materials and methods and Results sections are 82 introduced in Figure 1. Throughout the paper, and in accordance with CEHQ (2013a); IPCC 83 (2013), "simulation" or "climate simulation" refers to the raw climate model outputs. 84 "Scenario" or "climate scenario" refers to a post-processed simulation, which is a simulation 85 for which a series of specific choices have been made (study region and period, spatial and 86 temporal resolutions, bias-correction method). White boxes present how the climate 87 scenarios were obtained from 42 different bias-corrected climate simulations. Grey boxes 88 introduce the methodological framework proposed in this paper. It required computing CDIs 89 from climate data extracted from the aforementioned climate scenarios and HDIs from 90 simulated streamflows using a calibrated hydrological model. Afterwards, the statistical 91 relationships between CDIs and HD...