NEWS
The sensitivity of the catchment streamflow response to evaporative demand further supports the need for removal of invasive alien plants which heighten the evaporative losses . SAEON researchers and students are continuing to do hydrology research in the Kromme catchment with the aim of improving hydrological modelling for change prediction .
Further reading
Figure 4 : Monthly rainfall , PET ( expressed as a negative value ) and the rain-PET deficit shown with estimated monthly streamflow from the Kromme catchment ( Kromrivier Dam reservoir inflow ).
Figure 5 : The area supports fruit orchards , dairy and small stock farming .
• DWS ( Department of Water and Sanitation ) ( 2020 ). Algoa Water Supply System Operational Analysis 2020 – 2012 : August 2020 Monthly Monitoring Report .
• DWS ( 2011 ). Water Reconciliation Strategy Study for the Algoa Water Supply Area ( Pretoria , South Africa : Aurecon for Department of Water and Sanitation ).
• Hargreaves , G . and Samani , Z . ( 1985 ). Reference Crop Evapotranspiration from Temperature . Applied Engineering in Agriculture 1 , 96 – 99 .
• Kendall , M . G . ( 1975 ). Rank Correlation Methods , 4th edition , Charles Griffin , London .
• Mann , H . B . ( 1945 ). Non-parametric tests against trend , Econometrica 13:163 – 171 .
• Lynch , S . D . ( 2003 ). Development of a Raster Database of Annual , Monthly and Daily Rainfall for Southern Africa ( Pretoria , South Africa : Water Research Commission ( WRC )).
• NMBM ( Nelson Mandela Bay Municipality ) 2020a . Nelson Mandela Bay Municipality Dam Levels . https :// www . nelsonmandelabay . gov . za / damlevels
• NMBM ( Nelson Mandela Bay Municipality ) 2020b . Nelson Mandela Bay Municipality Notice : Restrictions on the Use of Water 87 – 09 September 2020 . https :// nelsonmandelabay . gov . za / DataRepository / Documents / water-restrictions- 9-september-2020 _ y66k4 . pdf
• Schulze , R . E . and Maharaj , M . ( 2004 ). Development of Database of Gridded Daily Temperature for Southern Africa ( Pretoria , South Africa : Water Research Commission ( WRC )). values observed in mid-2018 when a very large rainfall event in September 2018 helped the system rebound .
We can only hope that happens again soon for some short-term relief ; however , the longer-term analyses and modelled climate predictions do suggest a continuing drier future for this region on average . This should be accounted for in planning going forward .
Figure 6 : Nelson Mandela Bay ’ s second-biggest supply dam , the Impofu Dam , has reached critical levels ( Image : NMBM ).
Grassroots Vol 20 No 4 December 2020 20