The water of East African rift lakes contains large amounts of dissolved chemicals such as carbon dioxide, methane greatly and others like  phosphate, silicate, Sulfate, Sulfide, Iron, Ammonia, Alkalinity etc. Lake Kivu is a large, deep rift basin lake located in the western branch of the East African rift zone that contains a methane gas deposit of great economic interest with two main sources: Inorganic carbon dioxide CO2 + 4H2 = CH4 + 2H2O and Organic methanogenesis CH3COOH =CH4 + CO2. Lake Kivu is a stratified, meromictic lake bordering Rwanda and the Democratic Republic of the Congo (DRC). The lake has a surface area of 2,370 Km2, a volume of 580 Km3 and a maximum water depth of 485 m. To characterize the vertical variation of Lake Kivu water chemistry, 8 samples of water were collected using Niskin bottles in Lake Kivu near Gisenyi town. Water samples were therefore collected at different depths: 0 m, 40 m, 90 m, 240 m, 290 m, 340 m, 340 m, and 390 m. Hatch kits were used to analyze  water chemistry of samples taken of Sulfate, Sulfide, Iron, Ammonia, Alkalinity, Silica, PO4,andphosphorus.The results revealed that alkalinity  increases in the monimolimnion part due to the precipitation of calcium carbonate in the upper levels of the water column and dissolution in the monimolimnion. The conductivity, dissolved oxygen, temperature and pH weremeasured by CTD Sonde. Water column data from these studies showed increasing concentrations with depth. The divide between the mixolimnion and monomolimnion is estimated at a depth of around 40 m. Higher amounts of silica observed closer to the shoreline is likely a result of an influx of siliciclastic sediment and increased silica with depth is likely a result of the dissolution of diatoms below the photic zone. Keywords: Monimolimnion, mixolimnion, water stratification, chemicals agents.

Rwanda hosts million tons of peat deposits and that of western province is of great importance as it close to Kivu Lake. The discovery of methane gas in Kivu Lake has attracted investors in methane gas utilization as source of power supply and Compressed Natural Gas (CNG). Researchers identified Kivu Lake and adjacent area as an area of interest for hydrocarbon exploration. However, organic geochemical prospecting for hydrocarbon and energy content assessment is inadequate for the identified areas. The study aimed at determining the organic geochemistry of peat deposits in southwest, Rwanda. Forty (40) subsurface peat samples (1 to 10 m depth) were collected, air-dried and pulverized and screened. Five (5) samples with high organic matter content were subjected to biomarkers analysis using GC-GCMS. The n-alkanes distribution comprised mainly n-C11 to n-C 37. The Pr/Ph ratios (3.3-10.4, the waxiness index (0.09-0.87), CPI (3.6-7.8), OEP (3.5-6.0), C29 steranes (63.0–100.0%), C28 (0.0–28.0%), C27 (0.0–18.0%) and C27/ C29 sterane ratios (0.0-0.28). The ββ/ (ββ + αα) and 20S/ (20S + 20R) are 0.5 and 0.46 respectively. The C30 -moretane/ C30 -hopane ratios ranged from 1.56 to 2.42, while the oleanane index ranged from 0.07 to 0.26. The Ts/ (Ts + Tm) ratios ranged from 0.13 to 1.05. The dominance of C-29 sterols and C29/C27 sterane ratio which ranged from 3.5 to 100 indicating derivation from terrigenous higher plant material. The Pr/Ph ratio (>3) reflect the oxic to sub-oxic environmental condition during peat deposition. The peat deposits in Western Province, Rwanda are very rich in organic matter of mainly terrestrial precursor deposited in dry and cold climate.

A hot spring is a hot water source that naturally occurs on the surface of the Earth from underground; it is typically heated by subterranean volcanic activity and the local underground geothermal gradient. There are four main hot springs in Rwanda, such as: Kalisimbi, Bugarama, Kinigi, and Nyamyumba, formerly named Gisenyi hot springs. It is often believed that soaking in a hot spring is a great way to naturally detox human skin. This research focuses on the geochemical analysis of Nyamyumba hot springs, located near the fresh water supply of Lake Kivu, with the purpose of understanding its healing capacity and safety. The Nyamyumba hot springs are located in the western branch of the East African Rift System, near the Virunga volcanic complex, which explains the rising and heating mechanism of the water. The concentrations of sulfate, iron, ammonia, silica, and phosphate, and the conductivity, alkalinity, and salinity of the water were measured using standard procedures. The results showed that the hot spring water has higher concentrations of chemicals compared to the Lake Kivu water, and the geochemistry of these hot springs may be associated with rock dissolution by hot water. The measured parameters were compared with World Health Organization (WHO) standards for recreational waters, and it has been identified that the Nyamyumba hot springs are safe to use for swimming and therapeutic activities.

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