Impacts of the Mississippi River spillway opening on faecal coliform concentration in Lake Pontchartrain

This study focuses on explaining the role of the periodic opening of the Bonnet Carré Spillway on the faecal coliform levels in Lake Pontchartrain. Water quality data were collected by the Lake Pontchartrain Basin Foundation to analyse the faecal coliform bacteria levels, turbidity, salinity, temperature, and dissolved oxygen in the lake water. The results show that the faecal coliform concentrations were lower during the spillway opening than the preceding and subsequent months. Statistical analysis shows the dilution effect, characterized by an effective reduction in faecal coliform concentrations due to increase in water turbidity, coupled with decrease in water salinity and dissolved oxygen because of spillway opening. It is also indicated that the combine effect of more than one factor produces a significantly greater reduction in the faecal coliform than each factor acting independently. Periodic spikes in faecal coliform concentrations were observed at sampling points located near the outlets of streams and drainage canals with high settlement densities. A positive correlation (r = 0.78467) was found between the average faecal coliform counts and average monthly precipitations, highlighting the role of precipitation run‐offs. The results of this study indicate that the spillway opening contributed to a reduction in the faecal coliform concentration in the lake's surface water during the studied periods.     

Bacterial indicators of faecal pollution in the waters of the El-Kabir River and Akkar watershed in Syria and Lebanon

Water samples for bacterial analyses were taken, when possible, at 41 sites in Lebanon and Syria in the El‐Kabir River watershed. Samples were analysed for total coliform (TC), faecal coliform (FC) and faecal streptococcus. The Lebanese samples also were analysed for the presence of sulphate‐reducing bacteria. The TC and FC concentrations were extremely high throughout the watershed, rendering the water unfit for any human uses. The origin of the bacteria is the untreated sewage waste from the numerous settlements situated throughout the watershed. This primary origin is supported by high ratios of FC/faecal streptococcus, although impacts from animal wastes also were observed. The bacterial levels were higher in summer than in winter, indicating a high winter river flow that dilutes a relatively constant source of human sewage discharged to the system. Spring waters also exhibited elevated levels of bacteria, implicating surface land use and waste disposal practices upstream of the springs. The data clearly shows that human health is at a high risk and that strategies for improving water quality and protecting spring water must be expeditiously implemented.     

Identifying Temperature Thresholds Associated with Fish Community Changes in British Columbia,Canada, to Support Identification of Temperature Sensitive Streams

We collected fish samples and measured physical habitat characteristics, including summer stream temperatures, at 156 sites in 50 tributary streams in two sampling areas (Upper Fraser and Thompson Rivers) in British Columbia, Canada. Additional watershed characteristics were derived from GIS coverages of watershed, hydrological and climatic variables. Maximum weekly average temperature (MWAT), computed as an index of summer thermal regime, ranged from 10 to 23 °C. High values of MWAT were associated with large, warm, low relief watersheds with a high lake influence. Measures of community similarity suggested that the fish community changed most rapidly through a lower transition zone at an MWAT of about 12 °C and an upper transition zone at an MWAT of about 19 °C. These results were confirmed using existing fisheries inventory data combined with predictions of MWAT from a landscape‐scale regression model for the Thompson River watershed. For headwater sites in the Chilcotin River watershed (which drains into the middle Fraser River), the relative dominance of bull trout versus rainbow trout (based on inventory data) decreased with increasing predicted MWAT although the distinction was not as clear as for the Thompson River sites. The fish communities in these watersheds can be characterized in terms of very cold water (bull trout and some cold water species), cold water (salmonids and sculpins) and cool water (minnows and some cold water salmonids). The two transition zones (ca 12 and 19 °C) can be used to identify thresholds where small changes in stream temperature can be expected to lead to large changes in fish communities. Such clear, quantifiable thresholds are critical components of a management strategy designed to identify and protect vulnerable fish communities in streams where poor land use practices, alone or in combination with climatic change, can lead to changes in stream temperatures. Copyright © 2015 John Wiley & Sons, Ltd.     

Assessment and Use of Indicator Bacteria to Determine Sources of Pollution to an Urban River

Elevated levels of indicator bacteria within a river system represent a significant impairment to surface water quality in many urban areas within the Great Lakes watershed. Outfalls from combined sewer systems are assumed to be the major source of bacteria to streams in many of these urban areas, including the Rouge River of southeastern Michigan. Current remediation strategies largely disregard other potential sources, including water entering the river from its headwaters region, rural runoff, and contaminated groundwater. These other potential sources of bacterial pollution to the Rouge River were assessed and compared with bacteria contributed from combined sewer outfalls (CSOs). Fecal coliform (FC) and fecal streptococci (FS) densities were determined at 28 locations in the Rouge River Watershed during the spring and summer of 1997, 1998, and 1999. The mean levels of both indicator groups vary considerably along each branch of the river and show no correlation to CSO locations. The magnitude of both FC and FS levels are, in fact, frequently greater at sites upstream of the part of the river influenced by discharges from CSOs. The highest FC levels coincided with rainfall events, but FC levels at various sites along each branch of the Rouge River violated acceptable water quality standards (200 colonies/100 mL) at nearly 50% of the sites even during dry weather. Total suspended solids were moderately correlated with FC (r = 0.79) throughout the watershed, suggesting that solids may play a role in transporting bacteria into the Rouge River. The data depict a strong influence of upstream water and rural runoff on the water quality of the Rouge River. FC to FS ratios (FC/FS) suggest the primary source of bacteria throughout the watershed is from domesticated animals and wildlife and not from sewage derived from CSOs.     

Watershed Modeling to Assessing Impacts of Potential Climate Change on Water Supply Availability

Climate change could have impacts on hydrologic systems threatening, availability of water supply resources. In Illinois, regional water supply planning efforts are attempting to better understand potential impacts on low flow and surface water availability through analysis of hydrologic sensitivity to a range of climate scenarios. This paper explores the development, calibration and validation of Fox River watershed model using the soil and water assessment tool (SWAT) and the model’s application to assess impacts of potential climate change. The watershed model is calibrated and validated using daily flow records at three gauging stations. Automatic model calibration followed by manual refinement of parameter values was performed. Calibration results were generally good for monthly and annual time step but only satisfactory for daily simulations. Based on simulations of global climate models produced for IPCC fourth assessment report, climate scenarios were prepared by the Illinois State Water Survey for water supply planning initiatives in north-east and east-central Illinois. These scenarios showed ranges of temperature change between 0°C to +3.3°C and annual precipitation changes between −127 to +127 mm in the next 50 years, excluding the 5% extreme ends of those climate model simulations considered. Changes in climate were reflected using adjustments to the historical record, instead of using direct outputs from individual climate models. The watershed model was used to assess the impact of potential climate change. Application results indicate that annual precipitation change of 127 mm on average increases annual water yield and 7-day low flows by 28% and 19%, respectively. In contrast, a temperature change of +3.3°C results in average reductions of annual water yield by 13% and 7-day low flows by 10%. Seasonal effects were investigated through evaluation of changes in average monthly flows. Increasing precipitation resulted in significant changes in streamflows in late summer and fall months where as increasing temperature greatly affects winter flows due to snowmelt. The key implication is that climate change-induced variability of streamflows could have major impacts on water supply availability in the Fox River watershed and in particular, increased periods of drought could result in deficit of supplies during seasons of peak water use. It must be noted that this analysis does not examine the potential impacts of population growth and water use on water supply availability, which are also expected to have substantial influences in the region.     

System Dynamics Evaluation of Climate Change Adaptation Strategies for Water Resources Management in Central Iran

The Zayandeh-Rud River basin, Iran, is projected to face spatiotemporally heterogeneous temperature increase and precipitation reduction that will decrease water supply by mid-century. With projected increase (0.70–1.03 °C) in spring temperature and reduction (6–55%) in winter precipitation, the upper Zayandeh-Rud sub-basin, the main source of renewable water supply, will likely become warmer and drier. In the lower sub-basin, 1.1–1.5 °C increase in temperature and 11–31% decrease in annual precipitation are likely. A system dynamics model was used to analyze adaptation strategies taking into account feedbacks between water resources development and biophysical and socioeconomic sub-systems. Results suggest that infrastructural improvements, rigorous water demand management (e.g., replacing high water demand crops such as rice, corn, and alfalfa), and ecosystem-based regulatory prioritization, complemented by supply augmentation can temporarily alleviate water stress in a basin that is essentially governed by the Limits to Growth archetype.     

Riparian Forest Harvesting Effects on Maximum Water Temperatures in Wetland-sourced Headwater Streams from the Nicola River Watershed, British Columbia, Canada

Water temperature was continuously recorded during the ice-free season between June/July and October/November at 90 sites with lentic and lotic stream sources distributed throughout the Nicola River watershed (British Columbia, Canada) in 1999, 2000, and 2001. The eight lentic-sourced stream temperature monitoring sites were located in two adjacent watersheds. The headwaters and riparian areas around the wetland outlet of the treatment watershed were harvested during the overwinter period between 1999 and 2000. Areas around and downstream of the headwater wetland outlet in the control watershed were not harvested. Reducing riparian shade by harvesting activities increased maximum stream temperatures in the treatment watershed by up to 1–2°C relative to the control watershed. Because of the general downstream cooling trends in lentic-sourced headwater streams, riparian harvesting activities in these regions have a reduced thermal impact relative to similar harvesting alongside lotic-sourced headwater streams, whose maximum stream temperatures may warm by up to 8°C following harvesting. The downstream influence of elevated maximum stream temperatures from riparian harvesting of lentic-sourced headwater streams appears to be localized, but persists for at least 2 years following harvesting. Both lentic-sourced treatment and control streams in the current study relaxed towards baseline equilibrium temperature estimated by the lotic-sourced watershed trend within several hundred meters of downstream travel distance, with cooling rates proportional to the distance from expected thermal equilibrium. Due to the heating in wetland-sourced stream reaches adjacent to riparian harvesting, the regions downstream of treatment areas cool more rapidly than similar regions in control watersheds as the stream attempts to achieve thermal equilibrium.     

Snowpack response in the Assiniboine-Red River basin associated with projected global warming of 1.0 °C to 3.0 °C

This study assesses snow response in the Assiniboine-Red River basin, located in the Lake Winnipeg watershed, due to anthropogenic climate change. We use a process-based distributed snow model driven by an ensemble of eight statistically downscaled global climate models (GCMs) to project future changes under policy-relevant global mean temperature (GMT) increases of 1.0 °C to 3.0 °C above the pre-industrial period. Results indicate that basin scale seasonal warmings generally exceed the GMT increases, with greater warming in winter months. The majority of GCMs project wetter winters and springs, and drier summers, while autumn could become either drier or wetter. An analysis of snow water equivalent (SWE) responses under GMT changes reveal higher correlations of snow cover duration (SCD), snowmelt rate, maximum SWE (SWE_max) and timing of SWE_max with winter and spring temperatures compared to precipitation, implying that these variables are predominantly temperature controlled. Consequently, under the GMT increases from 1.0 °C to 3.0 °C, the basin will experience successively shorter SCD, slower snowmelt, smaller monthly SWE and SWE_max, earlier SWE_max, and a transition from snow-dominated to rain-snow hybrid regime. Further, while the winter precipitation increases for some GCMs compensate the temperature-driven changes in SWE, the increases for most GCMs occur as rainfall, thus limiting the positive contribution to snow storage. Overall, this study provides a detailed diagnosis of the snow regime changes under the policy-relevant GMT changes, and a basis for further investigations on water quantity and quality changes.     

Sampling and Modeling Approaches to Assess Water Quality Impacts of Combined Sewer Overflows—The Importance of a Watershed Perspective

As part of the planning effort for combined sewer overflow (CSO) abatement, a combination of sampling and mathematical modeling was used to characterize both CSO and receiving water quality in the city of Buffalo, NY. Samples collected during storm events showed that while CSOs within the city boundary are a source of fecal coliform to the Buffalo River, higher concentrations enter the river from the upper watershed, upstream of the city. Loading estimates of Pb, Zn, Cu, and Hg were made for design storms and on an annual basis using a combined model and sampling approach. While the metals loads were quantifiable from the CSOs, the loads associated with the upper watershed discharge were greater, for example, by a factor of 3 to 18 times for the design storms. Continuous, automated sampling of conventional parameters at 15 minute time steps indicated that the river experienced non-compliant periods for dissolved oxygen. In some cases, low dissolved oxygen levels may be associated with CSO inputs, but the hydraulics of the river system also had an important negative impact on dissolved oxygen. In developing CSO abatement options for the Buffalo River, it is essential to recognize that there are other significant contaminant sources in the upper watershed that will continue to negatively impact water quality.     

Nonpoint source reduction to the nearshore zone via watershed management practices: Nutrient fluxes,fate, transport and biotic responses — Background and objectives

Studies that evaluate the linkages between watershed improvement through Best Management Practices (BMPs) and downstream outcomes are few. Water quality of coastal waters is often impacted by soil and nutrient loss from watersheds in agriculture. Mitigation of these impacts is of concern in the Great Lakes, the Finger Lakes Region of New York State, and generally in water bodies of North America. In this issue, we report on hypothesis-based research at the watershed level evaluating the impact of BMPs on mitigation of nonpoint sources of nutrient and soil loss to streams and the nearshore zone of a lake. Specifically, we hypothesize not only reductions in nutrient and soil losses from watersheds but also a resultant decrease in metaphyton (filamentous algae), coliform bacteria, and macrophyte populations in the nearshore at stream mouths draining sub-watersheds where BMPs were introduced. Small experimental sub-watersheds, predominantly in agriculture (> 70%), were selected to ensure that effects on downstream systems would not be confounded by other land use practices often observed in large watershed approaches. In this introductory paper, we provide background information on Conesus Lake, its watershed, and the Conesus Lake watershed project, a large multi-disciplinary study evaluating agricultural management practices. The series of papers in this volume consider the effect of BMPs designed to control nonpoint sources on water chemistry, metaphyton, macrophytes, and microbial populations in the coastal zone of a lake. Ultimately, this volume expands the basic understanding of the ability of BMPs to control nonpoint source pollution while contributing toward the goal of improving water quality of downstream systems including streams, embayments, and the nearshore of large lakes.     

The utility of the AC/TC ratio for watershed management: a case study.

A human-impacted watershed was monitored during the dry summer seasons in 2002 and 2003 to investigate the impact of providing access to sewer mains to local village residences. Faecal coliform concentrations were monitored at select sites along the 30-mile stretch of creek, together with faecal streptococci, enterococci and total coliforms. Analysis of the results found that levels of faecal coliforms were inadequate at identifying significant known influxes of human and animal sewage established by sanitary survey. However, the bacterial ratio of atypical colonies to total coliform colonies (AC/TC), obtained from the total coliform membrane filter assay on m-Endo media, correctly indexed human faecal impact of inadequately sewered villages located along the creek. In addition, the AC/TC ratio correctly classified the predominant source of faecal runoff in the creek headwaters as agricultural, and indicated when aged agricultural faecal material was introduced by tributaries. An approach for watershed management that uses the AC/TC ratio in addition to levels of bacteria is proposed.     

Impacts of Climate Change on Water Resources Availability and Agricultural Water Demand in the West Bank

Global climate change is predicted as a result of increased concentrations of greenhouse gasses in the atmosphere. It is predicted that climate change will result in increasing temperature by 2 to 6°C and a possible reduction of precipitation of up to 16% in the Mediterranean basin. In this study, the West Bank is taken as a case study from the Mediterranean basin to evaluate the effects of such climate change on water resources availability and agricultural water demands. Due to the uncertainty in climate change impacts on temperature and precipitation, a number of scenarios for these impacts were assumed within the range of predicted changes. For temperature, three scenarios of 2, 4 and 6°C increase were assumed. For precipitation, two scenarios of no change and 16% precipitation reduction were assumed. Based on these scenarios, monthly evapotranspiration and monthly precipitation excess depths were estimated at seven weather stations distributed over the different climatic and geographical areas of the West Bank. GIS spatial analyses showed that the increase in temperature predicted by climate change could potentially increase agricultural water demands by up to 17% and could also result in reducing annual groundwater recharge by up to 21% of existing values. However, the effects of reduced precipitation resulting from climate change are more enormous as a 16% reduction in precipitation could result in reducing annual groundwater recharge in the West Bank by about 30% of existing value. When this effect is combined with a 6°C increase in temperature, the reduction in groundwater recharge could reach 50%.     

Heuristic Modelling of the Water Resources Management in the Guadalquivir River Basin, Southern Spain

A model comprising blocks of artificial neural networks (ANNs) combined in sequence was used to simulate the inflow and outflow in a water resources system under a shortage of water. We assessed the selection of appropriate input data using linear and non-linear cross-correlation functions and sensitivity analysis. The potential model inputs were flow, precipitation and temperature data from various gauging stations throughout the upper watershed of the ‘Guadiana Menor’ River (southern Spain), and the model considered various input time lags. The ANNs based on the selected inputs were effective relative to those with no relevant inputs, and produced more parsimonious models. We also investigated conceptual analogies inherent in the ANN models by analyzing the response profiles of the modelled variables (inflow and outflow) in relation to each of the selected input data. The results demonstrate that the neural approach approximated the behaviour of various components of the water resources system in terms of various hydrologic cycle processes and management rules. Our findings suggest that in dry periods a mean temperature increase of 1°C in low altitude locations of the region will result in a mean decrease of approximately 2% in the inflow to the water resources system, and a mean increase of approximately 12% in the outflow requirements for irrigation purposes.     

Drinking Water in the Hilly Region of Bangladesh: How Is the Quality?

This paper assesses the chemical and bacteriological quality of drinking water in three districts of the Chittagong Hill Tract (CHT), a region within Bangladesh. Drawing water samples from tubewells, chharas /springs, lakes/canals, wells, and ponds, analysis was done on pH, alkalinity, arsenic, phosphate (PO 4 ), sulphate (SO 4 ), ammonium-nitrogen, conductivity, and faecal coliform bacteria. The PO 4 and SO 4 concentrations were within the permissible limits. In contrast, 100% of the water samples contained alkalinity below 400 mg/l. Varied proportions, ranging from 14% to 50%, of tubewells, chharas /springs, lakes/canals, and well water had a pH of less than 6.5. Three out of 16 (18.8%) tubewell water samples tested had arsenic contamination and 18% of the chhara /spring and 11% of the well water samples had an unacceptable level of conductivity. In addition, faecal coliform bacteria contaminated almost all sources of water, ranging from 81% to 100%. The water used for drinking in CHT in general is harmful for health.     

Warming of the lower Columbia River, 1853 to 2018

Water temperature is a critical ecological indicator; however, few studies have statistically modeled century-scale trends in riverine or estuarine water temperature, or their cause. Here, we recover, digitize, and analyze archival temperature measurements from the 1850s onward to investigate how and why water temperatures in the lower Columbia River are changing. To infill data gaps and explore changes, we develop regression models of daily historical Columbia River water temperature using time-lagged river flow and air temperature as the independent variables. Models were developed for three time periods (mid-19th, mid-20th, and early 21st century), using archival and modern measurements (1854–1876; 1938–present). Daily and monthly averaged root-mean-square errors overall are 0.89°C and 0.77°C, respectively for the 1938–2018 period. Results suggest that annual averaged water temperature increased by 2.2°C ± 0.2°C since the 1850s, a rate of 1.3°C ± 0.1°C/century. Increased water temperatures are seasonally dependent. An increase of approximately 2.0°C ± 0.2°C/century occurs in the July–Dec time-frame, while springtime trends are statistically insignificant. Rising temperatures change the probability of exceeding ecologically important thresholds; since the 1850s, the number of days with water temperatures over 20°C increased from ~5 to 60 per year, while the number below 2°C decreased from ~10 to 0 days/per year. Overall, the modern system is warmer, but exhibits less temperature variability. The reservoir system reduces sensitivity to short-term atmospheric forcing. Statistical experiments within our modeling framework suggest that increased water temperature is driven by warming air temperatures (~29%), altered river flow (~14%), and water resources management (~57%).     

Using a weight-of-evidence approach for management of watersheds.

This research used a weight-of-evidence approach to evaluate sources of contaminants in a drinking water watershed that serves as part of the City of Boston's water supply. The approach incorporated land use analysis using GIS, sanitary surveys, traditional water quality monitoring and microbial source tracking (MST) tools. Case-study tributaries were selected based on elevated faecal coliform counts. Land use analysis and sanitary surveys were used to identify suspected microbial sources, including residential septic systems, agricultural animal operations, commercial/industrial operations and wildlife activity. Sampling sites were selected to hydrologically isolate potential contamination sources. Samples were collected seasonally over 1 year and analysed for traditional and MST parameters. Results demonstrated that both septic systems and a horse stable were contributing microbial loads in the first tributary. In the second tributary, septic systems from the townhouses were contributing microbial loads while a plant nursery was contributing organic matter. This evidence was used to evaluate best management practices to mitigate the contamination.     

大清河流域水循环影响因素演变特征分析

以海河流域的重要支流大清河流域为研究区,从气象因素和土地利用的角度对该流域水循环影响因素的演变特征进行分析。采用滑动平均法、Mann-Kendall非参数检验和小波分析法,分别对气象要素的趋势性、突变性和周期性进行了分析;同时,基于大清河流域四期的土地利用数据,分析了不同土地利用类型的演变规律。结果表明:(1)1970—2011年,大清河流域年降水量呈不显著的"减—增—减—增"的变化趋势,年均气温则变现为显著增加的态势;年潜在蒸散量在近54年来变化也较显著,呈"减—增"的变化;(2)流域年降水量几乎未发生突变,年均气温和年潜在蒸散量分别在1991年和1973年发生突变;(3)年降水量、年均气温以及年潜在蒸散量的演变周期分别以22年、28年和28年为主;(4)大清河流域土地利用类型以耕地、草地和林地为主,而土地利用类型的转化则处于耕地与城乡、工矿、居民用地,林地与草地之间。通过对大清河流域水循环影响因素演变规律的分析,可为进一步在该流域开展基于水循环理论的科学研究提供依据和支撑。     

Analysis of the effect of climate change on the Nakdong river stream flow using indicators of hydrological alteration

This study models the effect of climate change on runoff in southeast Korea using the TANK conceptual rainfall-runoff model. The results are assessed using the indicators of hydrological alteration (IHA) developed by U.S. Nature Conservancy. Future climate time series are obtained by scaling historical series, provided by four global climate models (GCMs, IPCC, 2007) and three greenhouse gas (GHG) emissions scenarios (IPCC, 2000), to reflect a maximum increase of 3.6 °C in the average surface air temperature and 33% in the annual precipitation. To this end, the spatio-temporal change factor method is used, which considers changes in the future mean seasonal rainfall and potential evapotranspiration as well as the daily rainfall distribution. In this study, the variance range for precipitation is from +3.55% to +33.44% compared to the present for years between 2071 and 2100. The variance range for the daily mean temperature is estimated between +1.59 °C and +3.58 °C. Although the simulation results from different GCMs and GHG emissions scenarios indicate different responses of the flows to the climate change, the majority of modeling results show that there will be more runoff in southeast Korea in the future. According to the analysis results, the predicted impacts of hydrological alteration caused by climate change on the aquatic ecosystem are as follows: 1) an increase in the availability of aquatic ecosystem habitats in Nakdong River in future summers and winters, 2) an increase in stress on the aquatic ecosystem due to extremely high stream flow, 3) an increase in the stress duration of flood events for the Nakdong River downstream and 4) an increase in aquatic ecosystem stress caused by rapid increases or decreases in stream flow.     

Stream Temperature Impacts Because of Changes in Air Temperature,Land Cover and Stream Discharge: Navarro River Watershed,California, USA

Stream temperatures are critically important to aquatic ecology, especially cold‐water fish such as salmonids. Stream temperatures are influenced by multiple factors, including local climate, solar radiation on the stream channel, stream discharge volume and groundwater contributions. The Heat Source hydrodynamic and thermodynamic numerical model was used to evaluate temperatures in three stream reaches in the Navarro River watershed, California, USA. The model was calibrated and validated for summer 2015 conditions and then applied to scenarios that address changes in air temperatures, riparian forest cover and stream discharge. Modelling results indicate that stream temperatures are sensitive to changes in air temperatures and riparian forest cover and that higher discharge volume mitigates those impacts. Modelled stream maximum weekly average temperatures (MWAT) increased by 1.5–2.3°C in response to an air temperature increases of 3.5°C under low flow conditions (drought) but by only 0.9–2.0°C under moderate flow. Complete removal of riparian forest in a large‐scale forest fire would increase MWAT by 2.2–5.9°C in low discharges and by 1.0–4.4°C under moderate discharge. Riparian zone reforestation would decrease MWATs by less than 0.8°C, a modest change reflecting high existing shade on the modelled stream reaches. Comparison of identical climate and land cover change scenarios under low and moderate discharge conditions reveals that efforts to conserve stream discharge volume could be an effective mechanism to mitigate stream temperature increases. Copyright © 2016 John Wiley & Sons, Ltd.     

Climate change projections of temperature and precipitation for the great lakes basin using the PRECIS regional climate model

The Great Lakes Basin plays an important role in the economy and society of the United States and Canada, and climate change in this region may affect many sectors. In this study, six GCM simulations were downscaled to resolve the Great Lakes using a regional climate model (RCM) with 25 km × 25 km resolution. This model was used to project changes in temperature and precipitation during the mid-century (2040–2069) and late-century (2070–2099) over the Great Lakes basin region with reference to a baseline of 1980–2009. The whole-basin annual mean temperature is projected to increase 2.1 °C to 4.0 °C above the baseline during the mid-century, and 3.3 °C to 6.0 °C during the late-century. Summer temperatures in the southern portion of the basin are projected to increase more than the temperatures in the northern portion of the basin; whereas winter temperatures are projected to increase more in the north than in the south. Estimates of the whole-basin annual precipitation with respect to the baseline vary from −3.0% to 16.5% during the mid-century and −2.9% to 21.6% during the late-century, respectively. Future summer precipitation in southwestern areas of this region is expected to decrease by 20%–30% compared to the baseline, but winter precipitation (mostly snow) is expected to increase by 11.6% and 15.4% during the mid-century and late-century. This study highlights the effects of the large expanses of water (such as the Great Lakes) on regional climate projections and the associated uncertainties of climate change.