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The United States loses almost 3 tons of topsoil per acre per year. [16] 1 inch (2.5 cm) of topsoil can take between 500 [17] and 1,000 years [18] to form naturally, making the rate of topsoil erosion a serious ecological concern. Based on 2014 trends, the world has about 60 years of topsoil left. [18] [19]
Sand or gravel aquifers would thus be easier to extract water from (e.g., using a pumping well) because of their high transmissivity, compared to clay or unfractured bedrock aquifers. Hydraulic conductivity has units with dimensions of length per time (e.g., m/s, ft/day and ( gal /day)/ft 2 ); transmissivity then has units with dimensions of ...
The bulk density of soil depends greatly on the mineral make up of soil and the degree of compaction. [3] The density of quartz is around 2.65 g/cm 3 but the (dry) bulk density of a mineral soil is normally about half that density, between 1.0 and 1.6 g/cm 3.
For example, GW-GM corresponds to "well-graded gravel with silt." If the soil has more than 15% by weight retained on a #4 sieve (R #4 > 15%), there is a significant amount of gravel, and the suffix "with gravel" may be added to the group name, but the group symbol does not change. For example, SP-SM could refer to "poorly graded SAND with silt ...
The Universal Soil Loss Equation (USLE) is a widely used mathematical model that describes soil erosion processes. [1]Erosion models play critical roles in soil and water resource conservation and nonpoint source pollution assessments, including: sediment load assessment and inventory, conservation planning and design for sediment control, and for the advancement of scientific understanding.
A poorly-graded soil is a soil that does not have a good representation of all sizes of particles from the no. 4 to no. 200 sieve. A poorly-graded gravel is classified as GP, while a poorly-graded sand is classified as SP. Poorly-graded soils are more susceptible to soil liquefaction than well-graded soils. [1]
Field capacity is the amount of soil moisture or water content held in the soil after excess water has drained away and the rate of downward movement has decreased. This usually occurs two to three days after rain or irrigation in pervious soils of uniform structure and texture.
One can also calculate the expected speed of sound for a given fluid; this can be compared to the speed of sound empirically measured by an ultrasonic flowmeter for the purposes of monitoring the quality of the flowmeter's measurements. A drop in quality (change in the measured speed of sound) is an indication that the meter needs servicing.