REPORT. Impact on Irrigated Land by the Proposed 765kV Perseus-Hydra Transmission Power line

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Domenic Hodges
8 years ago
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1 Rehab Green cc Registration No: 2002/094339/23 PI Steenekamp PO Box Queenswood 0121 Pretoria Cell: Fax: Report No: RG/2007/05/14/1 Date: May 2007 REPORT Impact on Irrigated Land by the Proposed 765kV Perseus-Hydra Transmission Power line (Addendum to Environmental Impact Assessment Report, P.I. Steenekamp, (Scoping document) Requested By ARCUS GIBB (Pty) Ltd Compiled By Rehab Green Monitoring Consultants CC Environmental and Rehabilitation Monitoring Consultant cc P.I. Steenekamp (Cert.Sci.Nat.)

com Report No: RG/2007/05/14/1 Date: May 2007 REPORT Impact on Irrigated Land by the Proposed 765kV Perseus-Hydra Transmission Power line

2 CONTENTS Page 1. TERMS OF REFERENCE 3 2. METHODOLOGY STUDY RESULTS CONCLUSION RECOMMENDATION.. 4 REFERENCES FIGURES: Figure 1: Localities of intersections. Page 2 of 6

3 1. TERMS OF REFERENCE Rehab Green Monitoring Consultants cc was requested by ARCUS GIBB (Pty) Ltd to assess the impact on irrigated areas along the proposed Perseus-Hydra 765 kv alternative routes as follows. Quantification of existing irrigation that would be affected by each alternative route and the effects of the alternatives on future irrigation plans (related to soils and availability of irrigation water). On the basis of this information, rank the alternatives in respect of impact on irrigation agriculture. Provide more detail about irrigation agriculture, including the problems associated with transmission towers in irrigation lands and what restrictions there are if any on ongoing irrigation. These issues are addressed in the soil impact assessment report (scoping document) by P.I. Steenekamp, 2005 for the alternative routes proposed at that stage. However, the major impact on irrigated land by power lines is the obstructions of irrigation systems such as centre pivots. Suitable locations for the erection of centre pivots are also bound to suitable soil types and often further obstructed by roads, farm boundaries, farm houses etc. Such restrictions often prevent the use of such systems at full capacity which seriously hamper the economic viability of such a system. Such obstructions often lead to low productivity of high potential land or even total withdrawal of land which can not be utilized effectively with preferred irrigation systems. One tower placed at the wrong position can therefore permanently prevent the use of a centre pivots at a specific place. The proposed route dated 14/11/2006 as supplied by ARCUS GIBB deviate to some extent from the previous 3 alternative routes and therefore a reassessment of the impact of irrigated land was done. 2. METHODOLOGY The impact on irrigated areas was determined by superimposing the alternative route on the national land cover data layer. All intersections with irrigated areas were extracted and the length was calculated. 3. STUDY RESULTS Four intersections of irrigated areas were identified and shown in Figure 1. Table 1 gives the distance/length of each intersection as well as the coordinates of the centre point in a projected and geographic format. Table 1: Locality and Intersection length of Irrigated Areas Intersection Number Land Cover/ Land Use Description Distance of Intersection (m) Centre point coordinates of intersection Projected, Wgs, LO25 Geographic Wgs Y X X Y 1 Cultivated, commercial, irrigated Cultivated, commercial, irrigated Cultivated, commercial, irrigated Cultivated, commercial, irrigated Page 3 of 6

Quantification of existing irrigation that would be affected by each alternative route and the effects of the alternatives on future irrigation plans (related to soils and availability of irrigation

4 4. CONCLUSION The length of intersections 1, 2 and 3 varies between 294 and 665 meters. The intersections cuts through the edges of irrigated lands (mainly centre pivots) according the land cover layer and can be avoided by slight deviation of the line direction and/or manipulations of the positions of towers. The length of intersection 4 is 2891 m and might not be possible to avoid obstruction of centre pivots by manipulation of the position of towers or minor deviation of the line direction. It however appear that the proposed route cuts through a narrow corridor on the edges of a number of centre pivot units. 5. RECOMMENDATIONS Obstruction of irrigation systems at intersections 1, 2 and 3 can probably be avoided by proper spacing of towers and/or minor deviations of the line direction. A much more prominent corridor between centre pivot units occurs approximately 1 km east of the current proposed route which can be considered at intersection 4. A proper and detail field assessment should be done at large irrigated areas to determine the most suitable route to minimize the impact. Towers without anchor lines should be used to decrease the area of impact. Keeping routes along farm boundaries and roads will definitely decrease the impact in most cases because irrigation systems seldom stretch across farms or roads. It will also largely prevent obstruction of possible future irrigation developments. REFERENCES Thompson M.W, South African National Land-cover Database Project Data Users Final Report (Phase 1, 2 and 3), Pretoria: CSIR Environmentek (1999). Page 4 of 6

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