ALCOM's Surface Water Body Database for SADC1 |
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more than just a list of dams, lakes and swamps 1 Southern African Development Community <> 2 Aquatic Resource Management Programme for Local Communities
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Lieven Verheust Introduction More than 14,000 water bodies have been inventoried in eleven countries and more data are being added daily. Database fields include geographical, administrative, meteorological, socio-economic, physical and chemical data as well as data on the use of the water body, presence of plant and animal species and fishing activity. Additional, supplementary information is generated by linking to other existing databases with other fields, using uniform identifiers. Since 1996, the SWB database has been integrated in a geographical interface which has enabled a multitude of applications in various disciplines: hydrology, agriculture, fisheries, health, environment or general development. Besides the SWB digital map, which holds the point data for all geo-referenced water bodies, the database is now also adding polygon data for a number of water bodies as well as polygons of all watersheds in SADC. |
Sources of data Information and grey literature from: |
For Zimbabwe alone, the information in the core fields (name, geographical
references and size) was compiled from more than 10 different sources. Information on
other specialised fields is gathered from specific literature, much of which is classified
as "grey" literature. Continuous contacts with the different sources of
information is also ensuring a regular update on new information from these sources. New
dams are still being constructed, new research is being conducted, fisheries statistics
are being collected continuously and the new information is entered in the database when
it becomes available. Both reservoirs and natural water bodies larger than one hectare (ha) are included in the inventory. Since most of the SWBs in SADC are reservoirs, a number of the data fields (e.g. dam wall data) are only valid for these water bodies. The following conditions have to be met for a water body to be included in the inventory:
Data fields included in the main database The main database includes more than 95 fields subdivided in geographical, administrative, meteo-rological, socio-economic, physical and chemical data as well as data on the use of the water body, presence of plant and animal species and fishing activity. A list of the fields included in the main database and the number of current entries in each field are given in Table1. Linking to other existing databases with different fields (such as databases with time series on fish production) provides more details on water bodies and the geographical entity to which these water bodies belong (districts, provinces, countries,etc.). Calculation of other variables (such as Morpho Edaphic Index), overlay with digital maps (such as elevation, temperature, rainfall,etc.) and modelling provide additional information on each water body. |
Collected data At present, data from eleven countries have been collected (Table 2). Supplementary data are still expected from Botswana, South Africa (only big reservoirs included at the moment), Tanzania, Zambia and Zimbabwe. Integration into a geographical interface and GIS (Geographic Information System) Entries with latitude and longitude data have been integrated in a geographical interface. The integration of the database into a GIS is used to generate more data and to enable studies that require geographical analysis. It is possible to zoom into a certain area of SADC and click on displayed points or polygons (water bodies) to get more information about these bodies (Figure 1). One can also display one water body or a set of water bodies based on their characteristics from the database. This has been made possible using a combination of two simple and affordable software packages in the Windows environment by a transfer of unique identification numbers of the database program to the mapping program and vice versa. Application of the database as a decision support tool Modules are being developed in the database to function as a decision support tool for policy-makers, government services and non governmental organizations. Applications are numerous and only a limited number of them are described below. Note that most of the described modules are still in the planning or development phase. Planning of new dams
Monitoring of filling and drying of dams
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Table 1 Characteristics and summary statistics on main fields in the SWB database
Nr. |
Field name |
Field description |
No. of entries |
1 |
SADC ID |
SADC Database Identification Number |
14,240 |
2 |
Nat ID |
National Database Identification Number |
14,240 |
3 |
Nat_Index |
Index in national database (if applicable) |
12,450 |
4 |
Name |
Name of the water body |
4,525 |
5 |
Latitude |
Latitude (in decimal degrees) |
11,442 |
6 |
Longitude |
Longitude (in decimal degrees) |
11,442 |
7 |
Grid_Ref |
Map grid reference |
11,719 |
8 |
Map_Nr |
Map number |
11,286 |
9 |
Coord_South |
Coordinates south (in any format |
798 |
10 |
Coord_East |
Coordinates east (in any format) |
798 |
11 |
UTM_Zone |
UTM zone number |
0 |
12 |
UTM_Coord |
UTM coordinates |
0 |
13 |
Rivername |
Name of the main river(s) which feed(s) the water body |
1,054 |
14 |
Sub-catchment |
Name of the sub-catchment |
99 |
15 |
Main catchment |
Name of the main stream catchment |
0 |
16 |
Division |
Division in which the water body is situated (if applicable) |
10,560 |
17 |
District |
District in which the water body is situated |
12,617 |
18 |
Province |
Province or Region in which the water body is situated |
9,667 |
19 |
Country |
Country in which the water body is situated |
14,240 |
20 |
International |
Is the water body shared by different countries? |
13,715 |
21 |
Owner |
Unit which controls the water body or name of owner |
1,011 |
22 |
Ownertype |
Type of ownership |
884 |
23 |
Surf. area |
Full supply surface area |
9,342 |
24 |
Capacity |
Full supply capacity |
9,418 |
25 |
Maxdept |
Maximum depth |
600 |
26 |
Meandepth |
Mean depth |
8,478 |
27 |
Catch. area |
Catchment area of the water body |
443 |
28 |
pH |
Average pH value of surface water |
347 |
29 |
Conductivity |
Average conductivity of surface water |
350 |
30 |
Transparency |
Average Secchi Disk value |
349 |
31 |
Alt_min |
Altitude - Min of range |
646 |
32 |
Alt_max |
Altitude - Maximum of range |
646 |
33 |
Permanence |
Is the water body permanent or seasonal? |
647 |
34 |
Rainmin |
Mean annual rainfall - minimum of range |
598 |
35 |
Rainmax |
Mean annual rainfall - maximum of range |
598 |
36 |
Soiltype |
Main soil type of the catchment of the reservoir |
1 |
37 |
Type |
Type of water body (Lake, Swamp or Reservoir) |
3,305 |
38 |
Constr_Yr |
Construction year of the dam |
2,690 |
39 |
Wallheight |
Height of the dam wall |
768 |
40 |
Condition |
Dam wall condition |
572 |
41 |
Siltation % |
Estimated percentage of dam silation (volume %) |
565 |
42 |
Breached or silted |
Is the dam breached or completely silted? |
304 |
43 |
Fenced |
Is the damwall fenced ? |
1 |
44 |
Access |
Access by road |
432 |
45 |
Dist.vill |
Distance from the nearest village |
73 |
46 |
Main use |
Main use of the water body |
555 |
47 |
Domestic |
Is the water body used for domestic water supply? |
246 |
48 |
Irrigation |
Is the water body used for irrigation? |
6,560 |
49 |
Livestock |
Is the water body used for livestock watering? |
323 |
50 |
Municipal |
water Is the water body used for municipal water supply? |
280 |
51 |
Bricks |
Is the water body used for brick construction? |
6 |
52 |
Industry |
Is the water body used for industrial purposes? |
97 |
53 |
Fishing |
Is the water body used for fishing? |
69 |
54 |
Other use |
Any other use of the water body? |
1,717 |
55 |
Fish |
Presence of any fish in the water body |
51 |
56 |
Stocked |
Was the water body stocked with fish ? |
24 |
57 |
Microph.bream |
Presence of microphageous tilapia (bream) |
241 |
58 |
Macroph.bream |
Presence of macrophageous tilapia (bream) |
98 |
59 |
Clarias |
Presence of Clarias sp. |
193 |
60 |
Labeo small |
Presence of small Labeo sp.like L. cylindrus,... |
28 |
61 |
Labeo big |
Presence of Big Labeo sp. like L. capensis, umbratus, altivelis,... |
5 |
62 |
Barbus small |
Presence of small Barbus sp. like B. paludinosus,... |
86 |
63 |
Barbus big |
Presence of big Barbus sp. like B. holubi, marequensis,... |
3 |
64 |
Carp |
Presence of carp (common, chinese,...) |
50 |
65 |
Eel |
Presence of Anguilla sp. |
1 |
66 |
Bass |
Presence of Micropterus sp. |
31 |
67 |
Tigerfish |
Presence of Hydrocynus vittatus |
1 |
68 |
Lepomis |
Presence of Lepomis macrochirus. |
8 |
69 |
Lungfish |
Presence of Protopterus sp. |
1 |
70 |
Other fish |
Presence of other non-determined fish species |
20 |
71 |
Crocs |
Presence of crocodiles |
394 |
72 |
Hyacinth |
Presence of water hyacinth (Eichornia crassipes) |
7 |
73 |
Hook and line |
Presence of hook and line fishing |
403 |
74 |
Traps |
Presence of trap fishing |
0 |
75 |
Sport |
Presence of sport fishing |
0 |
76 |
Gill net |
Presence of gill net fishing |
0 |
77 |
Seine nets |
Presence of seine net fishing |
0 |
78 |
Fisherfolk |
Number of net fishers |
53 |
79 |
Nets |
Number of gill nets used (1 net = 100m2 mounted) |
16 |
80 |
Boats |
Number of boats/canoes/vessels |
45 |
81 |
Catch/yr |
Total yearly fish catch |
75 |
82 |
Comments |
Any observations or comments on data collection or water body |
3,077 |
83 |
Date |
Date of record (visit to water body) |
11,174 |
84 |
Lat/Long generation |
Source of the Lat/Long date |
10,750 |
85 |
Source of data |
Source of Data |
11,713 |
86 |
Orig_ID |
ID in original database |
525 |
87 |
Orig_Ref |
Reference source in original database |
525 |
88 |
Dupe_ID |
SADC ID of possible duplicate record |
0 |
89 |
Main_ID |
SADC ID of water body where this water body belongs to |
0 |
90 |
Nat region |
Natural region (if applicable, currently Zimbabwe only) |
447 |
91 |
Hydrozone |
Hydrozone (if applicable, currently Zimbabwe only) |
10,564 |
92 |
Subzone |
Subzone (if applicable, currently Zimbabwe only) |
10,551 |
93 |
Locality |
Locality (if applicable, currently Zimbabwe only) |
10,413 |
94 |
ZimOT |
Ownertype (used in Zimbabwe database only) |
10,566 |
95 |
ZimDT |
Division Type (Zimbabwe only) |
10,562 |
96 |
Reliability |
Reliability of Source data (ZAR data only) |
503 |
Table 2. Number of entries per country for 3 important fields
Wildlife
Irrigation Analysis of potential for irrigation
Fisheries and aquaculture Choice of the right species to stock
Determination of fisheries potential
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Health Monitoring of water borne diseases such as bilharzia
Monitoring of water borne diseases such as malaria
General development and food security The fact that water is a prime factor in food security is widely recognised; however, it is not enough to monitor rainfall alone to predict harvests. Water storage is an equally important factor which influences food production. The module which monitors filling and drying of dams can be used to make early warning systems more complete in predicting shortfalls of harvests.
Figure 1. Information about a water body displayed on a clickable map
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Figure 2: Distribution of dams in Zimbabwe in relation <>to land use
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Figure 3: Watersheds affected by water hyacinth in Zimbabwe |
Future of the database Just like most databases, the SWB SADC database is very dynamic. Dams are continuously being constructed and related information added to the database. More information is being collected to complete fields for registered water bodies and fields are being added when there is a demonstrated need. New databases are also being linked to the main database as necessary. A number of data in time series require monthly or yearly inputs from the different SADC member countries. This underlines the need for an integration of the database management in a strong SADC structure that is able to fulfil these tasks. Finally the database has to be accessible to all interested parties to perform queries and analyses. Part of these queries could be satisfied by making a part of the database available on a WWW server where a simple search instrument could provide users with information on a selection of water bodies. HTML (Hyper Text Markup Language) also provides a graphic clicking interface which allows users to zoom into the geographical area of interest. The same interface can be used on WWW and on a local network. ALCOM has already made some information available on WWW and plans to make a large part of the database available later this year. More specialised queries and requests for analysis should be directed to the database management team which should be able to respond to all demands through the decision support module of the database. |
Figure
4. Coverage of the SWB database e-mail (Harare, Zimbabwe): alcom@ harare.iafrica.com Fax: 00263-4-736847 |