1 Current research activities at SAWS in relation to water resourcesChristina Botai; Lucky Ntsangwane; Joel Botai South African Weather Service March, 2017 Doc Ref no: SAWS-Rand-Water-Forum
2 Doc Ref no: SAWS-RES-Rand-Water-Forum.001.01Outline Introduction Overview of SAWS research units Applications development research scope Current research activities Current status of dams Water reservoirs recovery: Is it statistically realistic? Current seasonal forecasts Conclusion Doc Ref no: SAWS-RES-Rand-Water-Forum
3 Introduction The South African Weather Service (SAWS) is a public entity (SA Weather Service Act Number 8 of 2001) under the Ministry of Environmental Affairs. SAWS is a national meteorological service and a member of the World Meteorological Organization. SAWS provides two distinct services: Public Good Services (funded by Government) and Commercial Services (where the user-pay principle applies) Mandate: To ensure the ongoing collection of all meteorological data over South Africa and surrounding southern oceans for the use by current and future generations; including air quality and atmospheric monitoring To be the long-term custodian of a reliable national climatological records including national air quality data base To fulfill the international obligations of the Government of South Africa under the Convention of the WMO 3
4 The SAWS “Seamless” Forecasting SystemsObservations NWP GCM Coupled: GCM+ Ocean Tools -Satellite Radar Synops LDN Upper Air Regional (SADC) Local (SA) Mesoscale Ensembles (poor man’s) MOS Medium range (ECMF) Ensembles (NCEP) MOS -Ensembles -MOS -CCAM Ensembles -MOS -Ocean Models-GCM Ensembles > 2 Years Forecast Uncertainty 30 Days– 2 Years Days 4 -10 Days Outlook: -Rainfall and temperature anomalies -Rainfall and Temperature Tendencies -Climate Change Hours Outlook: -Rainfall & temperature anomalies Outlooks: -Potential hazardous weather events Rain and temperature anomalies 3-12 Hours Warnings: -Severe weather -Daily weather elements 0 – 2 Hours Products Detail Warnings: -Severe weather Disaster management, Hydrology, Public Disaster Man, Agriculture, Hydrology, Commerce Disaster Man, Public, Agriculture, Commerce Commerce, Agriculture, Health,Energy Commerce, Agriculture, Health, Energy Strategic planning Agriculture, Energy, Environment. Benefits Doc Ref no: SAWS-RES-Rand-Water-Forum
5 Value Chain of SAWS Operational ActivitiesClients Infrastructure Observations & Data Collection Data Processing & Archiving Products & Services Doc Ref no: SAWS-RES-Rand-Water-Forum 5
6 Applications Development ResearchApplications research Agro-meteorology Energy Health Hydro-meteorology Focus is the interaction of Weather/climate with Agriculture, hydrology, Energy, & Health Current research interests in Applications research Drought monitoring Soil moisture Run-off Stream flow Dam levels Water accounting at municipal levels Crop stress indicators Weather/Climate & infectious diseases Weather/climate & energy Doc Ref no: SAWS-RES-Rand-Water-Forum 6
7 Doc Ref no: SAWS-RES-Rand-Water-Forum.001.01Drought monitoring Drought is a complex slow-onset natural hazard whose impacts reverberate through many sectors of the economy such as water resources, agriculture, and natural ecosystems Southern Africa countries have been affected by the recent/current drought Drought monitoring is important for establishing e.g., drought early warning system prepare for and adopt appropriate measures for the mitigation of the anticipated changes Doc Ref no: SAWS-RES-Rand-Water-Forum
8 Drought Monitoring Indices/Indicators (DMI)Drought indices are used to provide quantitative assessment of the duration, severity, intensity and frequency (drought indicators) of drought events. Define a drought event (e) Set a threshold for severity i.e., SPI is continuously negative Determine start and end of a drought event Characterize the drought event by use of: DMI Duration (DD) Severity (DS) Intensity (DI) Frequency (DF) D 𝑺 𝒆 = 𝒋=𝟏 𝒎 𝑰𝒏𝒅𝒆𝒙 𝒋 𝒆 𝑫𝑰 𝒆 = 𝑺 𝒆 𝒎 Key: m: DD 𝑛 𝑠 : number of drought events 𝑁 𝑠 : Study epoch S: location 𝑫𝑭 𝒔 = 𝒏 𝒔 𝑵 𝒔 ×𝟏𝟎𝟎% Doc Ref no: SAWS-RES-Rand-Water-Forum
9 Drought Monitoring Indices/Indicators (DMI)Drought events are indicated when the results of SPI become continuously negative and reach a value of -1. Categorize drought (e.g., Tan et al., 2015) Level Drought category SPI/SPEI values Nil 0 ≤ index 1 Mild -1.0 < index < 0 2 Moderate -1.5 < index ≤ -1.0 3 Severe -2.0 < index ≤ -1.5 4 Extreme Index ≤ -2.0 Doc Ref no: SAWS-RES-Rand-Water-Forum
10 Drought Monitoring Indicators (DMI)Problem statement Drought impacts on Agriculture Intra-annual (inter-seasonal): SPI-3 Drought impacts on water resources Mid-term: Inter-annual: SPI-12 Social economic impact SPI-24 Study region RSA North West & Free state Data (monthly) TRMM ( ) District rainfall ( ) Doc Ref no: SAWS-RES-Rand-Water-Forum
11 Results (1): DMI (TRMM)
12 Results (5): DMI categorization (TRMM)Low mild droughts are occurred in the North West and parts of Free Sate provinces. Low moderate droughts occurred in the Northern Cape and parts of the Western Cape provinces but NW & FS and parts of EC exhibit high trends in moderate droughts. Low severity drought occurred in the Eastern Cape and parts of Northern Cape and North West provinces. Doc Ref no: SAWS-RES-Rand-Water-Forum
13 Results (3): DMI (Observations)NW experienced more frequent droughts reaching maximum and parts of FS with minimal DF but with a significant increase at the central part of the province. Droughts were more severe in parts of NW province as compared to the FS. NW experienced prolonged droughts as compared to FS (only central province). Droughts were least intense in both provinces with increasing tendency. Doc Ref no: SAWS-RES-AR-JAMSTEC-Seminar
14 Results (6): DMI categorization (Observations: 93 years)Mild droughts are observed in both provinces. Moderate droughts were experienced in the FS and NW. More severe droughts occurred in the FS than in the NW province. Extreme droughts reaching maximum in the FS minimal in the NW province. Doc Ref no: SAWS-RES-AR-JAMSTEC-Seminar
15 Precipitation concentration indexPrecipitation patterns and concentration vary according to regions and seasons. Changes in the precipitation total amount can result in environmental and economic effects. Information on changes in the intensity, patterns and concentration of rainfall can be used for accurate assessment of water resources, efficient water management and proper management of floods and droughts. Precipitation Concentration Index is used as a measuring tool to assess the spatial and temporal characteristics of precipitation concentration, variability and distribution. Data used: observations and satellite data 𝑃𝐶𝐼 𝑎𝑛𝑛𝑢𝑎𝑙 = 𝑖=1 12 𝑝 𝑖 𝑖=1 12 𝑝 𝑖 ×100 𝑃𝐶𝐼 𝑠𝑒𝑎𝑠𝑜𝑛𝑎𝑙 = 𝑖=1 3 𝑝 𝑖 𝑖=1 3 𝑝 𝑖 ×0.25 where 𝑝 𝑖 is the amount of precipitation of the ith month Classification of precipitation concentration based on PCI values PCI values Precipitation distribution < 10 Low monthly precipitation distribution over a year 11– 15 Moderate seasonal precipitation distribution 16 – 20 Irregular seasonal precipitation distribution > 20 High monthly precipitation distribution throughout the year
16 Precipitation concentration in South AfricaThere exists spatial and temporal variability in precipitation concentration across South Africa. Precipitation distribution ranges from relatively uniform to highly irregular Doc Ref no: SAWS-RES-AR-JAMSTEC-Seminar
17 Precipitation concentration in South AfricaPrecipitation distribution is uniform in summer; moderate in autumn and winter and highly irregular in spring. Doc Ref no: SAWS-RES-AR-JAMSTEC-Seminar
18 Water reservoirs monitoring: current statusSignificant increase in dam levels across all the provinces except the Western Cape and Eastern Cape. Doc Ref no: SAWS-RES-Rand-Water-Forum
19 Water reservoirs monitoring: current statusWMA also depict a significant increase in water levels, except the Berg and Breede. Doc Ref no: SAWS-RES-Rand-Water-Forum
20 Water reservoirs recovery: Is it statistically realistic?Area Dam Levels vs. Precipitation Dam Levels vs. Runoff Dam Levels vs. Evaporation Dam Levels vs. Streamflow R2 p-value Mpumalanga 40% 0.0005 31% 0.003 32% 0.0026 41% 0.0004 Limpopo 3.0% 0.395 0.4% 0.765 1.3% 0.57 6.1% 0.225 Gauteng 7.2% 0.184 9.8% 0.120 3.2% 0.381 11.8% 0.062 North West 2.8% 0.410 1.6% 0.544 4.9% 0.277 0.9% 0.635 Free State 1.9% 0.502 2.3% 0.460 14.1% 0.058 4.0% 0.332 Western Cape <<<0% 0.997 0.5% 0.744 0.7% 0.681 0.6% 0.714 Vaal Dam 6.2% 0.218 4.2% 0.317 17.7% 0.032 15.9% 0.0435 There exists a positive relationship between changes in dam levels and climatic variables. Streamflow and precipitation highly contribute to the changes in dam levels in Mpumalanga. Runoff contributes the least in Limpopo. Each variable contributes less than 1% in the Western Cape, with precipitation being the most least. Changes in the Vaal dam levels are highly attributed to evaporation followed by streamflow. Doc Ref no: SAWS-RES-Rand-Water-Forum
21 Water reservoirs recovery: Is it statistically realistic?Initial model: 𝑑𝑎𝑙~𝑝𝑟+𝑟𝑜+𝑒𝑣+𝑠𝑓 Area R2 p-value Final model Mpumalanga 57.6% 0.001 𝑑𝑎𝑙~𝑝𝑟+𝑟𝑜+𝑠𝑓 Limpopo 54.1% 0.002 𝑑𝑎𝑙~𝑝𝑟+𝑒𝑣+𝑠𝑓 Gauteng 17.8% 0.365 𝑑𝑎𝑙~𝑟𝑜 North West 7.4% 0.793 𝑑𝑎𝑙~1 Free State 20.0% 0.301 𝑑𝑎𝑙~𝑒𝑣 Western Cape 10.4% 0.659 Vaal 27.3% 0.136 𝑑𝑎𝑙~𝑟𝑜+𝑠𝑓 In Mpumalanga, climate variables account for 57.6% of the changes in dam levels. In Limpopo, climate variables account for 54% of the changes in dam levels. In the Vaal dam and Gauteng, the variables account for 27% and ~18% of the changes in dam levels, respectively. Climate variables account for 10% or less for the changes in dam levels in the NW, FS and WC provinces.
22 Is the future promising? Seasonal forecastsThe forecasting system indicates a significant amount of mixed forecasts across the country. As it is expected that there should be favourable rainfall conditions for the summer rainfall regions, isolated rather than widespread rainfall is likely for the early parts of autumn.
23 Is the future promising? Seasonal forecastsTemperature Forecasts show a tendency of above-normal temperatures with an increasing uncertainty. Temperatures, however drop towards winter across the country.
24 Doc Ref no: SAWS-RES-Rand-Water-Forum.001.01Summary Drought needs to be monitored in order to establish early warnings, prepare for and adopt appropriate measures to mitigate future changes. Current studies on drought monitoring suggest that South Africa is experiencing drought ranging from low mild to relatively severe. Monitoring precipitation distribution and concentration is essential in facilitating flow regulation. Current studies indicate that the country exhibits precipitation ranging from uniform, moderate and irregular seasonal distribution. Significant increases in dam levels are observed across all the provinces (but Western Cape) and Water Management Areas (except Berg and Breede). Variations in dam levels depend on among other factors climate variables such as rainfall, runoff, evaporation and streamflow. Rainfall seasonal forecasts indicates a significant amount of mixed forecasts across the country, with isolated rainfall expected for the early parts of autumn. Doc Ref no: SAWS-RES-Rand-Water-Forum
25 Doc Ref no: SAWS-RES-Rand-Water-Forum.001.01Thank you ! Doc Ref no: SAWS-RES-Rand-Water-Forum