Examples of Using Agrometeorological Models 2631

Models for soil erosion

Soil erosion is a natural phenomenon: it has occurred over the millennia as part of geological processes and climate change. However, erosion is more severe nowadays: soil degradation affects almost 2 billion ha of arable and grazing land (Table 26.2). More than 55% of this damage is caused by water erosion and nearly 33% by wind erosion.

Every year soil erosion and other forms of land degradation rob the world of 5-7 m ha of farming land and 2.5 billion tonnes of topsoil are washed away, tte United States lost about one-third of its topsoil since settled agriculture began. Worldwide, soil erosion puts the livelihoods of nearly one billion people at risk, tte effects of

Table26.2. Soil degradation by area and type (million ha) (www.fao.org).

Water erosion

Wind erosion

Chemical degradation

Physical degradation

Total

Asia

440

222

73

12

747

Africa

227

187

61

19

494

South-America

123

42

70

8

243

Europe

115

42

26

36

219

North and Central America

106

39

7

6

158

Southwest Pacific

83

17

1

2

103

Fig.26.1. Global status ofhuman-induced soil degradation (www.fao.org)

I1NMM11 I ml nr. Pc!

soil degradation

Wry high seventy

Nigh swerily

Moi er il e severity

Low Sfiinty

51 able land, ice cap or non-used

-v^leiird

Fig.26.1. Global status ofhuman-induced soil degradation (www.fao.org)

I1NMM11 I ml nr. Pc!

soil degradation

Wry high seventy

Nigh swerily

Moi er il e severity

Low Sfiinty

51 able land, ice cap or non-used

-v^leiird erosion are legion (Fig. 26.1). Soil washed off bare hillsides, ruins aquatic habitats and clogs waterways. Riverbeds rise, increasing the risk of floods. However, erosion can be reduced and eroded land can be restored.

Soil erosion is among the major environmental threats related to agricultural land use (Helming et al. 2005). Important European policies and directives, such as the Water Framework Directive, the European Commission Strategy for Soil Protection as well as agro-environmental measures address the issues of soil erosion. During recent decades, international research has greatly contributed to an improved understanding of soil erosion processes at various scales from single plots to complex watersheds. Research focus evolved from descriptive approaches over process analyses of soil-hydrological dynamics to in depth studies of the temporal interactions of rainfall and soil erosion, tte analysis of spatial dynamics of soil surface characteristics, runoff and erosion patterns is a recent topic of research, which is a crucial piece of the puzzle when analysing connectivity issues and when linking upland area processes of sediment production with channel processes of sediment transport.

Patterns of runoff and soil erosion represent the two-dimensional response of the landscape to rainstorm events, ttese patterns illustrate in a complex and yet incompletely understood way the spatial variability of important soil, land use and landscape characteristics, ttere has been increasing recognition of the significance of such patterns for understanding and predicting erosion and its environmental impacts. For example, improved insight into the way in which patterns of runoff and soil loss evolve over time and vary with spatial scale may help us to better comprehend the value and limitations of short-term plot studies with respect to erosion in a wider, real-landscape context. A better appreciation of the role of dynamic connectivity in runoff and sediment delivery may assist in improving our estimates and surface functions oflandscape response to rainfall events.

At present, numerous models for the estimation of soil erosion have been set up and some of them are available on-line (Table 26.3).

Table26.3. Examples of soil erosion simulation models. AGNPS (Agricultural Non-Point Source pollution model) AGNPS-UM (Agricultural Non-Point Source pollution model, modified) ANSWERS (Areal Nonpoint Source Watershed Environment Response Simulation) CREAMS (Chemicals, Runoff and Erosion from Agricultural Management Systems) EPIC (Erosion-Productivity Impact Calculator) EROSION-3D

EUROSEM (European Soil Erosion Model)

GLEAMS (Groundwater Loading Effects of Agricultural Management Systems) KINEROS2

LISEM (Limburg Soil Erosion Model) MEDRUSH

MOSES (Modular Soil Erosion System) project

MWISED (Modelling Within-Storm Sediment Dynamics) project (link down) RillGrow 1 and 2

RUSLE (Revised Universal Soil Loss Equation) SWAT (Soil and Water Assessment Tool)

USLE (Universal Soil Loss Equation)

- APSIM (Agricultural Production Simulator)

- TMDL (Total Maximum Daily Load)

- USLE-2D (Universal Soil Loss Equation 2D)

- USLE (MS Excel version)

- USLE-M (Universal Soil Loss Equation Modification)

- USPED (Unit Stream Power-based Erosion Deposition)

WATEM (Water and Tillage Erosion Model) WEPP (Water Erosion Prediction Project) GeoWEPP (Geo-spatial interface for WEPP) WEPP interfaces (US Forest Service)

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