CHAPTER 4 RESULTS AND DISCUSSION
4.3 Results from questionnaire (quantitative and qualitative) analysis
4.3.5 Section E: Key risks posed by the water quality in the Breede River
4.3.5.2 Risk of water quality impact on the quality of the crops/ products (QE4F)
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potential impact from poor management and maintenance of WWTW and the capacity of these facilities to treat the increased volumes of effluent from an increased population.
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acknowledged that they had no information on the upgrade and expansion plans for the WWTW and no data on the effectiveness of these facilities but are basing their concerns on water quality data collected by them and others for irrigation and drinking water for auditing purposes and the general perception that all WWTW in South Africa are under pressure.
The WWTW in the Upper Breede River (Worcester, Ceres and Wolseley) had high compliance levels (see section 4.2.4). However, the E. coli levels since 2018 did not reflect this improvement with the microbiological water quality downstream of Ceres regularly exceeding limits. The majority of participants indicated a medium to high risk related to the impact on the quality of the crops based. Farmers in the Upper and Middle Breede River section were concerned about the potential of E.coli pollution in the future.
Figure 4-44: Distribution of Farmer’s opinion on the impact of irrigation water quality on the quality of the crops/ products (QE4F).
Although there were concerns related to the potential impact of WWTW effluent and informal settlements not serviced and therefore by-passing formal WWTW, the majority of the participants indicated that the consequence of poor quality water for irrigation purposes on the current crop types cultivated in the Breede River is low. This is related to the fact that the water intended for irrigation is directed at the stem of the tree or vine and E. coli is therefore not likely to occur on the fruit itself. The impact on crops in the Breede River where vineyards, citrus and other fruit trees dominate was therefore not perceived to be high as water for irrigation purposes from micro-
0 10 20 30 40 50 60 70 80
A. Major positive impact
B. Minor positive impact
C. No impact D. Minor negative impact
E. Major negative impact
% participants
Impact of irrigation water quality on crop quality
2000 2020
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and drip irrigation systems are directed at the stems and the probability of fruit to be contaminated by E. coli considered to be relatively low as indicated by the comments: “As irrigation type differ between crops the risk of E. coli affecting the crops which are irrigated by drip irrigation is low as it is irrigated at the stem of the plant and not on the fruit itself” (F6) and “most crops will not be sprayed with water containing E. coli - vegetables might be impacted as irrigation is directly onto the product and not at the stem/ base” (F5). The potential for impacts in the future might be higher as commented: “Although not currently seen as a risk there is a future risk due to uncontrolled development in the urban areas of informal settlements and the risk of E. coli and the related impact on markets” (F4).
Most Farmers indicated that there is a low probability of the water quality impacting negatively on agricultural activities currently due to the way water for irrigation purposes is being managed.
However, there are concerns for crops where overhead irrigation is used as the potential for E.
coli contamination is high when water used for irrigation purposes is directed onto the leaves and vegetable/fruit crop itself.
Minor impacts were mainly linked to the increase in salt load in water purposed for irrigation and the impact that it would have depends on the type of crops cultivated. Most participants felt that the main crop, i.e. wine grapes, are relatively tolerant to an increased salt load and would therefore not be affected as much as for instance citrus and other fruit. In section 4.2 the increased salinity in parts of the Breede River has been highlighted. Farmers also highlighted the potential risk of increased salt levels (Na) impacting on crop quality and yield as indicated in the comment:
“Some crops are resistant to poorer water quality but there is a limit after which the quality of the crop will suffer. For instance wine grapes are salt tolerant to some extent but they will take time to recuperate after a period of irrigation with brackish water (during drought this happened as ground water was only source and it was either brackish or became brackish over time due to overuse and natural geology), if not the plant will suffer permanent damage (F2). However, the current practice of releasing water from the Brandvlei Dam is considered sufficient to dilute the salt load to a level acceptable for most crops. There is, however, a concern by Farmers that if the irrigation system in the Middle and Upper Breede River is not managed at the same standard in the future, there is a high probability of a major negative impact on the crop/ product quality.
The potential impacts of poor water quality on agriculture were highlighted in section 2.9. Not only is there an impact on crop yield and quality but the impact on irrigation infrastructure contributes to the cost of pollution to agriculture. The build-up of salts in soil and the impact thereof on the
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yield and crop quality is dependent on the crop type and the sensitivity of the crop to saline conditions in the soil. Grapevines were identified as sensitive to soil salinity (Moolman, 1999).