LAND SYSTEMS and LAND USE in the NWA PILOT SCHEME AREA

 

 

 

Land Use Planning Note AAH/14/87

 

 

 

CONTENTS

 

 

1 INTRODUCTION

 

2 EXISTING WORKING MATERIALS

 

2.1 Maps

2.2 LANDSAT

2.3 Previous Study

 

3 METHODS

 

4 LAND SYSTEMS

 

5 PRESENT LAND USE

 

6 LOCATION OF WATERYARDS (For Rehabilitation)

 

7 OBSERVATIONS on LAND USE

 

8 CONCLUSIONS

________________________________________________________________________________

 

1 INTRODUCTION

 

An area of some 3,000 odd square kilometres south of Ed Daein, with Abu Matariq approximately in the centre, was provisionally delineated as the area for the NWA Pilot Rehabilitation Scheme.

 

As a data base, until new satellite imagery is available, the Land Systems and Land Use within this area have been delineated, and extents measured, using materials presently available.

 

2 EXISTING WORKING MATERIALS

 

2.1 Maps

 

Sheets NC35-B and NC35-F of the 1986 Draft HTS/ODA Land Systems maps at 1:250,000 scale and the corresponding Sudan Survey Department map sheets dated 1976. [These maps should still be available in Nyala].

 

2.2 LANDSAT

 

Hardcopy of the two images Path 177 Row 52 and Path 177 Row 53 of LANDSAT 6, MSS (colour) at a scale of 1:250,000 dated November 1984.

 

2.3 Previous Study - HTS 1985

 

The report by HTS Ltd., titled "Mapping Land Use Change From LANDSAT Imagery: Result of a Pilot Study in Southern Darfur", contains some computer analysis of the area in question presented at a scale of 1:1 million.

3 METHODS

 

Land Systems and sub-systems were taken directly from the 1:250,000 scale maps, but it must be borne in mind that these data were all based on reconnaissance type studies.

 

For present land use attempts were made to extract information visually from the LANDSAT hardcopy. Results did not inspire any confidence - quality of the images, poor contrast and cloud cover - and this route was not pursued.

 

Computer analysis (HIPAS) of land use in 1984 were presented in HTS 1985 and data were extracted from this source. The scale, complex pattern and difficulties of delineating and measuring the minute areas does mean that the data so extracted are, at best, approximate.

 

4 LAND SYSTEMS

 

The land systems and sub-systems are shown in Figure 1. For simplicity sub-systems are shown by subscript (e.g. Qoz1 and Qoz2) of the system and the full mapping code is shown within Figure 1. [Nov 1999 - the Figure is not to hand].

 

Estimates of the various soils within the various land sub-systems are presented in Table 1 [Nov 1999 - the Tables referred to in this paper have not been located], these estimates being arrived at by following the assumptions:

 

         where 2 soils mapped, distribution is 80:20

         where 3 soils mapped, distribution is 60:30:10

 

Again it must be emphasised that these data are estimates and are based on reconnaissance studies.

 

5 PRESENT LAND USE

 

Study of the 1:1 million-scale computer analysis was done and two approaches taken. Firstly, various categories of land use were delineated and these are shown in Figure 2 [Again this figure is not available], and estimates of the extents shown in Table 2. The second approach was to separate out all land that was presently cultivated or fallow from other areas - the other areas being assumed to be grazing zones or tree covered (alluvial) areas, these data are shown in Figure 3 [Again this figure is not available] and Table 3.

 

6 LOCATION OF WATERYARDS (FOR REHABILITATION)

 

The ten wateryards provisionally selected for rehabilitation, by the NWA Adviser, are shown on Figures 1 and 4 and detailed in Table 4. It should be noted that the positions of wateryards number 7 and 8, Kunfusa and Shurshuri respectively, are questioned and exact locations require verification.

 

It should be noted that none of the wateryards lie in what would be generally recognised as typical Qoz (deep sands) and the yards within the Qoz Land System (Yards Numbers 8, 9 and 10) are shown to lie in the Qoz / Alluvial transition zone. Of these three yards No 8 appears to be located more on alluvium than Qoz, No 9 has scattered cultivation and alluvium with trees whilst No 10 is located in a zone of heavy cultivation. Wateryard No 10, Umm Seneina, is located close to what is mapped as deep (typical) Qoz.

 

Most of the other yards (Nos. 2, 3, 5, 6 and 7) appear to lie in what is recognised as alluvial areas without tree cover or with scattered cultivation. Yard No 1 (Sarhan) has some dense cultivation to the north and No 4 (Abu Matariq) is surrounded by scattered cultivation.

 

 

 

7 OBSERVATIONS ON LAND USE

 

7.1 The area delineated is not (1984), and has not been, as heavily cultivated as much of the land to the east, west and, particularly, north. The area around Ed Daein was almost 100% cultivated in 1984.

 

7.2 To the east and west of the delineated area there is a higher proportion of cultivated land to fallow land suggesting that either, there is greater pressure on the land causing a reduced fallow element, or the land is more fertile and can support heavier use.

 

It is assumed that the former reason is the explanation in that within the pilot area there are many morhaals and livestock has, in the past, been more important than arable farming and hence there has been less pressure on the land for arable use.

 

7.3 The most extensive heavily cultivated areas (1984) are to the north and east of Kiriu and along the northern boundary east and west of Sarhan, refer Figure 2. These areas do correlate with the more easily worked soils, Qoz and Atmur, and proximity to the large market centre of Ed Daein.

 

7.4 The whole area is inclined to show a scattered distribution of cultivation and fallow with a relatively high proportion of woodland and Nagaa - reflecting the complexity of the soil distribution pattern.

 

7.5 South of Abu Matariq cultivation decreases with distance into the alluvial areas though there is one relatively high density zone some 20 kilometres southwest of Abu Matariq. This area correlates with Atmur soils within Map Unit Bg2 on Figure 1.

 

7.6 Estimates of various land uses.

 

Land Use Type

Source

Square km.

Area predominantly cultivation + fallow

Table 2

763

Area predominantly cultivation + fallow

Table 3

643

Estimate of used* land within C3 and A3

Table 2

152

Estimate of gross (@) hand cultivable land

Table 1

1630

Estimate of net ($) hand cultivable land

/

1223

Useable land already cultivated**

/

915, or

75%

Notes * Assume 15% of C3 and 10% of A3 cultivated

@ Gross totals of Ae, Qa, At and Sq soils

$ Assume that 75% of gross is useable

** From 763 + 152 = 915 (using Table 2 data)

 

915

and ------ x 100 = 75%

1223

 

 

8 CONCLUSIONS

 

8.1 All the data presented for land use are approximate, four years old and must be used with caution.

 

8.2 There is a very complex pattern of land use that is related to soil distribution.

 

8.3 Arable use is noticeably less to the north, east and west of the presently delineated area. The area should probably be expanded to include some of the areas that are more heavily used.

 

8.4 An estimated 75% of the hand cultivable arable resource is / has been already cultivated.

 

8.5 The southern parts of the area (alluvial land systems) have very little land cultivated and would be considered as mostly grazing areas.

 

8.6 Most of the presently selected wateryards lie in areas that are not heavily cultivated.

 

8.7 Most of the cultivated area lies to the north of Abu Matariq.

 

8.8 Attempts to plot the alignment of known morhaals at the map scales presently available have proved very difficult and should await availability of materials of more suitable scale.

 

8.9 Most data could be more accurately determined once the 1:100,000 scale SPOT imagery is available. This imagery could also show quite a different picture (1987) due to accelerated use of land for arable cultivation during the past 3 to 4 years.

 

 

A.A.Hutcheon

21 December 1987