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Application of GIS and Remote Sensing for Assessing Watershed Ponds for Aquaculture development in Thai Nguyen, Vietnam.
Fourteen base layers (thematic maps) were used in the study and grouped into 4 main land use requirements for aquaculture: (1) potential for pond construction (slope, land use types, soil thickness, and elevation); (2) soil quality (soil types, soil texture, and soil pH); (3) water availability (distance to water, water sources, and precipitation); and (4) geographical and social economic status (distance to roads, population density, distance to local markets, and distance to hatcheries) (Table 1). Slope, elevation, soil type, soil thickness, precipitation, and local market centers and hatchery locations data were extracted from the digital topographic map of Dai Tu (1:25,000) (Vietnam Cartographic Publishing House, 1999). Land use types, roads, and hydrological systems data were taken from the topographic map and updated with SPOT satellite imagery acquired for 9 November 2002. Soil pH and soil texture were collected during the survey and extracted from soil information in Vietnam (Agriculture Publishing House, 2000). Population density data were taken from Statistical Yearbook of Thai Nguyen (Thai Nguyen Statistics Department, 2002).
Table 1: Land characteristics and rating rules used for assessing watershed pond for aquaculture development
| Parameters |
Suitability rating and score |
| Highly |
suitable a Suitable b Marginally suitable c |
Not suitable d |
| (4) |
(3) |
(2) |
(1) |
| Potential for pond construction |
|
|
| |
Slope |
< 5 |
>5 – 15 |
>15 – 25 |
> 25 |
| |
Land use types |
Paddy field |
Resident land, Unused land, Water body |
Agriculture land, Brushwood |
Planted and natural forest, Tea plants |
| |
Soil thickness (cm) |
>100 |
50-100 |
<50 |
---- |
| |
Elevation (m) |
<100 |
100-500 |
>500-1000 |
>1000 |
| |
|
|
|
| Soil quality |
|
|
|
| |
Soil types (FAO systems) |
Fluviols |
Haplic acrisols |
Haplic calcisols |
Humic Ferralsols, Rhodic ferralsols |
| |
Soil pH |
6-7 |
5-6 |
4-5 or 7-8 |
<4 or >8 |
| |
Soil texture (% clay) |
>35 |
18-35 |
<18 |
---- |
| |
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|
|
| Water availability |
|
|
|
|
| |
Distance to water body (m) |
<500 |
500-1000 |
>1000-2000 |
>2000 |
| |
Water sources |
Irrigation |
Rain-fed |
---- |
---- |
| |
Precipitation (mm/year) |
1500-2500 |
>2500 |
<1500 |
---- |
| |
|
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| Geographical and social economic |
|
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| |
Distance to road (m) |
<500 |
500-1000 |
1000-2000 |
>2000 |
| |
Population density (people/km2) |
>600 |
300-600 |
200-300 |
<200 |
| |
Distance to local market (m) |
<1000 |
1000-2000 |
2000-3000 |
>3000 |
| |
Distance to hatchery (m) |
<5000 |
5000-10000 |
>10000 |
---- |
- The highly suitable (HS = 4) level provides a situation in which minimum time or investment is required in order to develop fish farming.
- For a level classified as suitable (S = 3), modest time and investment are required.
- Marginally suitable (MS = 2), significant interventions may required before fish farming operations can be
conducted.
- The suitability level is not suitable (NS = 1), the time or cost, or both, are too great to be worthwhile for fish
farming.
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