Tuesday, March 23, 2010

Relationship between Soil erosion and Offsite Damage and its effect on water quality

Materials generated from agricultural activities can be carried into waterways by runoff and thus can negatively affect the watershed health. Also, sediment washing off crop land can fill reservoirs, harm aquatic plant life and degrade recreational resources. Moreover, suspended sediment and nutrients generated from farming are considered as most damaging sources to the environment. The conservation reserve program is designed to assist operators of agricultural land in conserving and improving the soil and water resources of their ranch. It is therefore expected that CRP will generate significant level of offsite water quality benefits.
To investigate the water quality benefits, we first need to analyze the costs of soil erosion on its environment. The affect of soil erosion is widespread in surrounding communities. In this blog, I try to investigate the relationship between soil degradation and its effect on water quality and water uses.

Links between soil erosion and offsite damage:
To evaluate the offsite benefits of CRP, we must need to understand the links between soil erosion and damage.

1. Loss of soil and nutrients
Rainfall erosivity
Soil characteristics
Crop management
Conservation practices
2. Movement of pollutants from Field to waterways
Watershed vegetation
3. Physical and biological effects on water quality
Dissolved oxygen
Sediment load
Nutrient concentrations
Fish populations
Algae levels
4. Use of water resources
Commercial fishing
Water storage
Drinking supplies
Industrial supplies
5. Value changes
Consumer surplus
Treatment costs
Avoidance costs

The relationship between soil erosion and offsite damage is complex in nature. In Figure 1, the first link mainly discuss about soil loss which is considered to be a function of rainfall erosivity, soil characteristics, crop management, conservation practices. Nutrients and pesticides are also carried off a field along with soil.
The second link signifies the amounts of sediment and chemicals that reach a waterway depend on distance, slope, and watershed vegetation of the watershed.

Physical measures of water quality include dissolved oxygen, temperature, sediment load, nutrient concentrations, fish populations, algae levels are categorized under third link. It mainly highlights the agricultural pollutants discharge into waterways and water quality.

The use of water resources is affected by the change in water quality. Water resources can be used as recreation, commercial fishing, navigation, water storage, drinking supplies, industrial supplies and irrigation.
Economic relationship between water quality changes and human activity can be expressed as changes in recreation demand, profit among water using industries.
To gauge the importance of the effects of soil loss on water quality, one needs to measure the benefits and costs to society of programs and policies designed to improve environmental quality. These measures are properly expressed in terms of changes in social welfare, defined as net changes in consumer and producer surpluses. Benefits or costs of water quality changes are measured through changes in economic welfare, represented by consumers and producers surpluses. A number of methods exist for deriving these measures, including revealed preferences, contingent valuation and averting behavior for consumer surplus and changes in production costs for producer surplus. Each of these methods can be applied properly to measure water quality benefits if related data sets are available.

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