Masinga Dam
The cache, a small screw-capped camo-pot, is hidden under bark pieces in a hole in the middle of a small tree.
To reach the cache location: take the A2 Nairobi-Thika road as far as Thika then exit on the slip road @ S1 02.416 E37 03.745 to join the A3 Garissa Road. Follow this as far as the B7 junction at S1 05.884 E37 40.150. Turn left (north) here and continue to the turn off for Masinga Dam @ S0 56.118 E37 40.598. Follow this broken tar/dirt road as far as the junction @ S0 53.220 E37 36.148. Turn left and head for the Masinga Dam Resort. After clearing gate security, park your cachemobile @ S0 53.527 E37 35.741. When ready, head back out of the entry gate and head left down the dirt road and around the c0rner down towards the lake at a boat landing @ S0 53.531 E37 35.559. From here head left (south) and follow the small track parallel to the lake shore through the trees to the cache.
The scenic 45km long and 120 sq.km Masinga dam is the largest man-made lake in east and central Africa and produces much of the hydroelectric power used in Kenya.
It is the first dam of the current five dams (Masinga, Kamburu, Gitaru, Kindaruma and Kaimbere) in the Tana River Seven Forks cascade hydropower complex and was completed in 1981. It is the main reservoir in the cascade with a capacity of 1.56 million cubic metres of water and is therefore used for water regulation throughout the year. A medium pressure system comprising two vertical Kaplan turbines drives two generators capable of generating 40 MW of power.
It is managed by the Tana and Athi Rivers Development Authority. The valley that it drowned has a convoluted shoreline and a number of islands. The maximum depth is 50m. The area is semi-arid.
The dam has a reservoir capacity (F.S.L) of 1056.5m above sea level. This is the Full Supply Level or the maximum amount of water it can hold before the spilling. Spillways are constructed to protect the dam walls from the immense pressure of increasing water in the dam and direct water out of the dam as a safety precaution.
Masinga Dam borders Yatta and Mbeere and stretches to Thika in the west. It holds marine life, fish, hippotamus and crocodiles. Much of its fish is 
supplied to Thika, Embu, Nairobi, Matuu and Masinga towns.
It affects the environment in the following ways. Flood water resulting from the two rainy seasons in the upper reaches of the river system is stored in a detention reservoir and released in the dry period as required, thus taming the natural supply of water, which fluctuates extremely, depending on the time of year, and retaining it for future use.
Optimum and steady loading of the downstream power plant turbines at Kamburu, Gitaru and Kindaruma is guaranteed, even in the long dry season, by releasing 2 x 45m3 of water/second through the Masinga turbines, which is the maximum theoretical flow normally. This figure also takes into account the infiux of the Thiba River at an average of 10 m3 per sec. and the capacities of the downstream continuous storage basins.
An additional 12,000 hectares of land could be irrigated within the reaches of the detention basin. Improved exploitation of the existing irrigation system in Bura Hola is achieved, since the amount of water supplied remains constant throughout the year, making it possible to have more than one harvest per year.
The upper reservoir capacity also provides for flood water protection, to a certain extent, for the lower course of the Tana River.
The 45-km-long and 120-sq-km large lake is the basis for creating a local fishing industry for Nairobi and the surrounding area.
Video links:
https://youtu.be/CNVo5wuOofY Masinga Dam full Dec 2011
https://youtu.be/c74IbMvmITU Masinga Dam closed June 2009
https://youtu.be/hW6nypOArSs and https://youtu.be/gNB30G9RZtY Masinga Dam overflowing April 2013
https://youtu.be/TDDLUTdSC34 April 2013, downstream flooding
https://youtu.be/1jCs3b7WOVU Masinga Dam full May 2010 (expansion plans)
https://youtu.be/EZAo_E5Z4OE Masinga Dam conservation plans
https://youtu.be/TJDGhmZ-jkQ Masinga Dam nearly full May 2010 (downstream evacuation plans)