Spatial and Temporal Dynamics of Key Water Quality Parameters in a Thermal Stratified Lake Ecosystem: The Case Study of Lake Mead

Abstract

Lake Mead located in the Arizona–Nevada region of the Mohave Dessert is a unique and complex water system whose flow follows that of a warm monomictic lake. Although monomictic lakes experience thermal stratification for almost the entire year with a period of complete mixing, the lake on occasion deviates from this phenomenon, undergoing incomplete turnovers categorized with light stratifications every other year. The prolonged drought and growing anthropogenic activities have the potential to considerably impact the quality of the lake. Lake Mead and by extension the Boulder Basin receive cooler flow from the Colorado River and flow with varying temperatures from the Las Vegas Wash (LVW), which impacts its stratification and complete turnovers. This study analyzes four key water quality parameters (WQPs), namely, total dissolved solids (TDS), total suspended solids (TSS), temperature, and dissolved oxygen (DO), using statistical and spatial analyses to understand their variations in light of the lake stratifications and turnovers to further maintain its overall quality and sustainability. The study also evaluates the impacts of hydrological variables including in and out flows, storage, evaporation, and water surface elevation on the WQPs. The results produced from the analysis show significant levels of TDS, TSS, and temperature from the LVW and Las Vegas Bay regions compared with the Boulder Basin. LVW is the main channel for conveying effluents from several wastewater treatment facilities into the lake. We observed an increase in the levels of TDS, TSS, and temperature water quality in the epilimnion compared with the other layers of the lake. The metalimnion and the hypolimnion layer, however, showed reduced DO due to depletion by algal blooms. We observed statistically significant differences in the WQPs throughout various months, but not in the case for season and year, an indication of relatively consistent variability throughout each season and year. We also observed a no clear trend of influence of outflows and inflows on TDS, temperature, and DO. TSS concentrations in the lake, however, remained constant, irrespective of the inflows and outflows, possibly due to the settling of the sediments and the reservoir capacity.

Measurement of Total Dissolved Solids and Total Suspended Solids in Water Systems: A Review of the Issues, Conventional, and Remote Sensing Techniques

“…Total dissolved solids (TDS) and total suspended solids (TSS) are two physical water quality parameters (WQPs) that impair the quality of water resources such as rivers and lakes [1][2][3]. Both TDS and TSS are fractional constituents of "total solids" of the same sample separated by filtration [4].…”

“…Increased concentrations of TDS and TSS in water bodies limit them from serving their purpose for drinking, power generation, industrial cooling, supporting biodiversity, ecosystem services, recreation, transportation routes, waste disposal, agriculture production, irrigation, energy production, regional planning, and fish farming [7][8][9][10][11][12][13][14][15][16][17]. Impairment of water bodies by parameters such as TDS and TSS is caused by climate change, development, and urbanization associated with surface imperviousness resulting from increased population, and contamination caused by rapid and uncontrolled environmental changes including drought, wastewater discharges, nutrient pollution, sediments, and changes in land use and land cover which results in negative impacts such as the proliferation of harmful blue-green algae, accelerated eutrophication, and extreme turbidity among others which have negative implications on the sustainability of the limited water resources [3,6,[18][19][20][21][22][23][24][25][26][27][28][29].…”

A Machine Learning Approach for the Estimation of Total Dissolved Solids Concentration in Lake Mead Using Electrical Conductivity and Temperature

“…Lake Mead, which lies on the Colorado River, is the largest reservoir in the Mohave Desert, Arizona-Nevada region in the Colorado River Basin (CRB) [1][2][3]. The lake is a crucial source of water for more than 25 million people in the southwestern US.…”

“…Some of these anthropogenic are unintended consequences that need to be minimized [8]. TDS-related economic damages to the CRB are estimated to be over USD 300 million per year, destroying millions of acres of irrigated lands [2,3,[9][10][11][12].…”

“…TDS is a known physical WQP [3,13,14], categorized by the United States Environmental Protection Agency (US EPA) in its secondary drinking water regulations (SDWRs) with an allowable limit in drinking water set to 500 mg/L [3,12,15]. These SDWRs are described as nonenforceable federal guidelines that cause cosmetic and aesthetic effects.…”