There is no physical container at GZ
Questions that need to be answered in order to log a find:
1. What is Porosity?
2. Where is Ground Water stored?
3. What sort of rock do you believe Fresnos ground water flows through?
4. Was there any water in the basin today?
At the listed coordinates you will find a canal and a storm basin park, both of which help to replenish the underground aquifers. This Earth Cache will help you better understand the geology behind aquifers and why they are so important.
An aquifer is defined as a body of rock or unconsolidated sediment that has sufficient permeability to allow water to flow through it. Unconsolidated materials, such as those in the Fresno Area, like gravel, sand, and even silt make relatively good aquifers, as do rocks like sandstone. Other rocks can be good aquifers if they are well fractured.
Groundwater is stored in the open spaces within rocks and within unconsolidated sediments. Rocks and sediments near the surface are under less pressure than those at significant depth and therefore tend to have more open space. For this reason, and because it’s expensive to drill deep wells, most of the groundwater that is accessed by individual users is within the first 100 m of the surface. Some municipal, agricultural, and industrial groundwater users get their water from greater depth, but deeper groundwater tends to be of lower quality than shallow groundwater, so there is a limit as to how deep we can go.
Porosity is the percentage of open space within an unconsolidated sediment or a rock. Primary porosity is represented by the spaces between grains in a sediment or sedimentary rock. Secondary porosity is porosity that has developed after the rock has formed. It can include fracture porosity — space within fractures in any kind of rock. Some volcanic rock has a special type of porosity related to vesicles, and some limestone has extra porosity related to cavities within fossils.
Since the Fresno/Clovis area was settled, most of the water supply for its people and businesses has come from the groundwater aquifer. Decades of reliance on groundwater has created a condition of groundwater overdraft. We have historically taken out more water than we have put back. Though supply has changed due to the Cities’ construction of surface water treatment plants to take pressure off of the groundwater aquifer, significant demand is still put on our groundwater supply. As population grows – now at roughly 650,000 in Fresno and Clovis – counting storm and surface water as the precious resources they are is more important than ever.
Replenishment through recharge
Our area’s groundwater overdraft would be even more serious, if not for the decades of inter-agency collaboration to constantly put water back in the ground. Groundwater supplies are recharged using surface water from rain and from the Kings and San Joaquin Rivers.
Rain that falls on the Fresno/Clovis area is moved through a network of pipelines to the 153 District stormwater basins throughout the urban area, where it slowly percolates through the soil to the groundwater aquifer.
Kings and San Joaquin River surface water allocations of the Cities of Clovis and Fresno, and Bakman Water Company are moved through Fresno Irrigation District canals to nearly 90 stormwater basins, for the purpose of groundwater recharge.
Shown below are the 10 years’ worth of storm and surface water volumes recharged in District basins. Keeping precious water in our area for future use is an important function of the District’s urban basin system. The collaborative work done with the Cities of Clovis and Fresno, Bakman Water Company, and with the Fresno Irrigation District contributes significantly to the volume of groundwater returned to the aquifer, and is part of the year-round, multi-agency effort to replenish groundwater supplies.
FTF:BilHarzia