Module 6 - Soil Erosion Flashcards
What are the three categories of water erosion?
Sheet and Rill erosion. Ephemeral gullies.
Sheet Erosion
Detachment and transport of thin layers of soil over a surface plane.
Rill Erosion
The detachment and transport of soil in shallow channels at a depth shallower than gullies.
Ephemeral gullies
Concentrated flow erosion is the detachment and transport of soil in channels. When these channels are shallow enough to be filled by normal tillage, these channels are referred to as Ephemeral gullies.
Aggregate stability also depends upon the presence and type of cations in the soil. Large amounts of sodium, potassium, and magnesium deflocculated soil colloids, preventing aggregation. On the other hand, Polyvalent cations, such as calcium, iron, and aluminum, promote flocculation.
True
Soil Loss Tolerance
Defined as the maximum level of soil erosion that will permit a high level of crop productivity to be sustained economically and indefinitely. How much soil loss is acceptable. The standard range used by NRCS is from 1 to 5 tons per acre per year.
RUSLE (Revised Soil Loss Equation)
The RUSLE uses the same factors as the USLE, but it was computer-driven with hardcopy tables also available. The developers of the RUSLE refined and improved on the accuracy of the USLE.
RUSLE2
RUSLE2 is Windows-based, it is more user-friendly, and it is improved over RUSLE version 1 and the USLE. There is better integration of K, C, and P over the season or over time. Major components of the RUSLE2 include a computer program to solve mathematical equations, a user interface, and a database from which the user selects inputs in order to best describe the field being assessed. RUSLE2 is based upon a combination of mathematical equations, scientific knowledge, and technical judgment.
WEPP (Water Erosion Prediction Project)
WEPP was the first model not based upon USLE technology. It is a process-based, daily simulation model. WEPP makes daily computations of the status of soil and biomass, that is to say, plant cover. When it rains, WEPP computes runoff, detachment, transport, and deposition. It has broader uses than does the USLE. At one time it was expected to replace RUSLE. The WEPP model consists of three components or sub-models. There is a climate generator, a hydrology component, and a plant-growth model. It also includes four databases, for climate, soil, tillage, and plant cover or crop.
CREAMS
The model Chemicals, runoff, and erosion from agricultural management systems, or CREAMS, was developed for use on small watersheds. It is used to assess nutrient losses on sediment and in the runoff. The following inputs are required: Topography, soil erodibility, potential runoff, cover management, and climate data.
EPIC
The EPIC model is the Erosion Productivity Impact Calculator. It is used to predict the long-term effects of soil erosion on productivity. It is also used to estimate the management practices needed to control losses. The model includes components on climate, runoff, soil erosion, soil moisture, soil chemistry, crop growth, crop and soil management, and economics. It computes erosion from a single point in the field.
AGNPS
The Agricultural non-point source or AGNPS model is used to estimate water runoff quality from agricultural watersheds. It handles a range in area from 5 to 50,000 acres. It predicts runoff volume, peak flow rates, eroded and delivered sediment, N and P in runoff, oxygen and inorganic chemicals.
