Application of remote sensing technology in researching and mapping drought map in Lang Son province


Posted at: 11:07:16 05/07/2016 - Read: 213
Từ khóa Key words: drought, GIS

Drought is a regular phenomenon appears and occurs in several geographical regions. In recent years, the drought situation in our country is getting fierce in intensity and expanding in scope and frequency. It’s seriously affecting agriculture, forestry and threatening the life of people. Drought is also one of the main causes of land degradation; therefore, identifying the drought area is one of the main task to assess and renovate the degradation land. In the framework of the project " Investigating the degradation land in Lang Son province", the Geoinformatic research center of Thai Nguyen University of Agriculture and Forestry has used GIS technology to identify the drought areas and decentralize the drought level for each commune, district of Lang Son province as follow:

Figure 1: The diagram of mapping drought land area

The fieldwok was performed in 309 surveying locations which were choose throught the climate features, irigation model, the land characteristics, vegetation cover, and other indicators then we can identify the drought areas of each commune, district in surveying map. The attribute information of each land parcel will be imported to the drought map.

The drought index for each month is determined by following  function:

Drought index (Kth) = K1 =Evaporation volume (E0(th)) / precipitation (R(th))

In which:

K(th): Drought index

R(th): The average precipitation each month

E0(th): The average evaporation volume each month

The Evaporation volume (E0) is determined according to the empirical formula of Ivanop as following:

 E0 = 0,0018 x (T+25)2 x (100-U)

T: air temperature (0C)

U: the relative air humidity (%)

According to the table of drought land decentralization, determining the number of drought months in each measuring stations. Next, we calculate the drought index (K1) for each month; if the drought index greater than 1, that month is considered as drought month, then calculate the total drought month of each measuring stations.

Table 1: Decentralizing and evaluating the drought land area base on drought index and month

No

Drought levels

Drought months

Drought index (K1)

Symbol

1

No drought

< 2

< 1

KhN

2

Low level drought

≥ 2 - 3

≥ 1 - 2

Kh1

3

medium level drought

≥ 3 - 5

≥ 2 - 4

Kh2

4

high level drought

≥ 5

≥ 4

Kh3

After that, decentralizing the drought month of each measuring station according to table 1. From the result, performing a spatial interpolation in ArcGIS software to determine the effected areas (the IDW tool is intergrated in ArcGIS software).

Using digitizing tools in ArcGIS software to digitize the boundaries and define the effected scope from measuring stations. The data which was degited is the drought level  areas containing the attribute data of 4 different drought level.

Using overlay tool in ArcGIS to overlay the drought data into the land parcels to build a drought map. The result is the drought map that containing the land parcel with different drought levels as following:

Figure 2: The drought map of Lang Son in 2015.

 

 

Posted by: GIRC

GeoInformatics Center - Thai Nguyen University of Agriculture and Forestry

Address: Quyet Thang commune, Thai Nguyen city, Vietnam | Tel: +84904.031.103

Email: girc.tuaf@gmail.com | Website: www.girc.tuaf.edu.vn