Hydrogeochemical evolution of inland lakes’ water: A study of major element geochemistry in the Wadi El Raiyan depression, Egypt

Abstract

Wadi El Raiyan is a great depression located southwest of Cairo in the Western Desert of Egypt. Lake Qarun, located north of the study area, is a closed basin with a high evaporation rate. The source of water in the lake is agricultural and municipal drainage from the El Faiyum province. In 1973, Wadi El Raiyan was connected with the agricultural wastewater drainage system of the Faiyum province and received water that exceeded the capacity of Lake Qarun. Two hydrogeological regimes have been established in the area: (i) higher cultivated land and (ii) lower Wadi El Raiyan depression lakes. The agricultural drainage water of the cultivated land has been collected in one main drain (El Wadi Drain) and directed toward the Wadi El Raiyan depression, forming two lakes at different elevations (upper and lower). In the summer of 2012, the major chemical components were studied using data from 36 stations distributed over both hydrogeological regimes in addition to one water sample collected from Bahr Youssef, the main source of freshwater for the Faiyum province. Chemical analyses were made collaboratively. The major ion geochemical evolution of the drainage water recharging the El Raiyan depression was examined. Geochemically, the Bahr Youssef sample is considered the starting point in the geochemical evolution of the studied surface water. In the cultivated area, major-ion chemistry is generally influenced by chemical weathering of rocks and minerals that are associated with anthropogenic inputs, as well as diffuse urban and/or agricultural drainage. In the depression lakes, the water chemistry generally exhibits an evaporation-dependent evolutionary trend that is further modified by cation exchange and precipitation of carbonate minerals.

A Series of Data-Driven Hypotheses for Inferring Biogeochemical Conditions in Alkaline Lakes and Their Deposits Based on the Behavior of Mg and SiO2

“…thus contains an array of collection procedures, which can be found in the referenced papers [8,28,29,62,67,68,75,76,[92][93][94][95][96][97][98][99][100][101]. Ten previously unpublished samples were included in the database.…”

“…The original data can be found in the "a" labeled tab of the spreadsheet, from [8,29,67,75,76,[95][96][97][98][99][100]. Where silica concentration was reported in Si (mg/L) it was converted into SiO 2 .…”

“…If the original units of mg/L were not given, our calculations assumed that values were reported relative to the standard mg/L HCO 3 − and were converted into meq/L on that assumption. This applies to data from Mohamed et al [98]. Charge balance error was calculated for every sample and expressed as a percentage using: A magnitude of CBE ≤ ±5% is typically considered acceptable, but for the sake of inclusion and acknowledging the challenging nature of analyzing alkaline lake samples, we used all data with CBE ≤ ±10% in Figures 4 and 5.…”

“…The wealth of alkaline lakes on Earth today has made it possible to create a comprehensive database of lake water chemical analyses. This data set (described in more detail in Appendix D) contains unpublished analyses from Canadian lakes and published analyses from various authors over the past 100 years [8,28,29,62,67,68,75,76,[92][93][94][95][96][97][98][99][100][101] detailing locations including Last Chance and Goodenough Lakes (Canada), Lake Yoa waters and brines (Chad), Bolivian Salars (Bolivia), Lake Eyasi Basin (Tanzania), Lerai (Tanzania), Pastos Grandes (Bolivia), Lake Van (Turkey), and Lake Neusiedl (Austria). Collected fluid samples include not only lake waters but also fluid chemistry data for associated springs, groundwaters, porewaters, and inflowing rivers and streams (which presumably represent source fluids).…”

Groundwater physico-chemical properties and water quality changes in shallow aquifers in arid saline wetlands, Ouargla, Algeria

“…The study of shallow aquifer vulnerability in arid regions with respect to high evaporation rates, and increased contamination from agricultural, domestic or industrial sources has been the subject of several recently published research (Amharref et al 2007;Omosuyi and Osehale 2012;Mohamed et al 2015). It is currently accepted that the combination of the three aforementioned effects (i.e., water-rock interactions, aerated water conditions and lithological heterogeneity within the watershed), coupled with low precipitation, lead to increased water mineralization and eventual salt paragenesis within the endorheic region beneath the stream bed in the unsaturated zone of a shallow groundwater system.…”