HYDROLOGICAL SITUATION REPORT for major rivers and dams in Botswana
Prepared by: Hydrology and Water Resources Division Tel: +267 3607439
TABLE 1: DAMS FULL CAPACITY OR VOLUME
Name of Dams River Name Capacity in Safe Yields in Mm3 (Million Mm3 (Million cubic meters) cubic meters)
Gaborone Notwane 144.150 9.4* Shashe Shashe 87.900 25.3* Molatedi Marico 200.786 Letsibogo Motloutse 104.00 24 Nnywane Nnywane 2.280 0.6 Bokaa Metsimotlhabe 18.500 4.9 Moshupa Moshupa 0.690 Ntimbale Tati 26.370 3.6 Dikgatlhong Tati/Shashe 400 62 Lotsane Lotsane 42.5 6.6 Thune Thune 90 10 * Based on pre-siltation volumes TABLE 2: THE AMOUNT OF WATER IMPOUNDED IN EACH DAM ON THE SAME MONTH
CURRENT YEAR 2015 PREVIOUS YEAR 2014 VOLUME(%) VOLUME(%) WEEKLY CUMULATIVE 48th week 48th week by NAME OF THE INFLOW INFLOW VOLUME November VOLUME November DAM DATE (m3 x 106) (m3 x 106) (m3 x 106) 2015 DATE (m3 x 106) 2014 1 GABORONE 25-Nov-15 0.608 1.081 3.698 2.62 25-Nov-14 9.850 6.98 2 SHASHE 24-Nov-15 0.000 0.000 68.104 77.48 25-Nov-14 63.800 72.58 3 MOLATEDI 23-Nov-15 0.320 0.501 10.214 5.09 11-Sep-14 70.826 35.27 4 LETSIBOGO 25-Nov-15 0.000 0.000 38.600 37.12 24-Nov-14 75.920 73.00 5 NNYWANE 25-Nov-15 0.573 0.573 1.600 70.18 25-Nov-14 1.345 58.99 6 BOKAA 25-Nov-15 2.090 8.762 9.140 49.41 25-Nov-14 3.833 20.72 7 NTIMBALE 24-Nov-15 0.671 0.671 22.050 83.62 24-Nov-14 21.970 83.31 8 DIKGATLHONG 24-Nov-15 0.000 0.000 291.49 72.87 25-Nov-14 346.85 86.71 9 LOTSANE 17-Nov-15 0.000 0.000 21.62 50.87 25-Nov-14 31.77 74.75 10 THUNE 24-Nov-15 0.000 0.000 34.106 37.90 25-Nov-14 45.593 50.66 Gaborone and Bokaa dams received very little THE WEEKLY OBSERVATION OF AMOUNT OF WATER IN PERCENTAGES increases in dam volumes this week, with IN EACH DAM: A COMPARISON OF THE 2014/15 & 2015/16 VOLUMES (%) Gaborone dam receiving 0.608m3*106 and Bokaa 90.00 2.09m3106. Molatedi dam in South Africa also continued to receive some inflows. The water 80.00 shortage crisis experienced in the greater 70.00 Gaborone area continue to persist despite the inflows. Therefore greater Gaborone is still 60.00 reliant on the North South Carrier scheme 50.00 supply from Dikgatlhong dam and Letsibogo dam 40.00 which are in the northern part of the country 30.00 where better rainfall amounts are experienced (%) VOLUME annually, and also the Masama well fields. Only 20.00 the dams in the southern part experienced 10.00 inflows or increase in volumes this week, whereas the dams in the northern region did not 0.00 G SH M LE N B NT DI L TH have any inflows. A A O TSI N O IM K O U NAMES OF DAMS B SH L B Y K B G TS N O E AT O W A A AT A E Latest update, 27th -November-15. R E G A A LE LH N O DI O N O E N E N E G VOLUME(%) 48th week November 2.62 77.48 5.09 37.12 70.18 49.41 83.62 72.87 50.87 37.90 2015/16 VOLUME(%) 48th week November 6.98 72.58 35.27 73.00 58.99 20.72 83.31 86.71 74.75 50.66 2014/15 MAJOR RIVER, Figure 1
Okavango Delta at Mohembo The 2015/16 hydrological year has started with the lowest flows as compared to previous 1200 years since 2010/11 hydrological year. Looking at the graph and the trend since 2010/11, there has been gradual drop in flows in every 1000 successive year which suggests that we may have a drop in flows this hydrological year
800 2010/11 unless we experience a 5 year return period 2011/12 flood to have something that looks similar to 2012/13 2013/14 2010/11 hydrological year. The 2015/16 600 2014/15 hydrological year flows continue to drop 2015/16 further even at a point where it is expected to Dischargem3/s in Bankful Dischrage 400 start rising, looking at the flow trends from previous years' flows. th
Latest update, 27 November-15. 200
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MAJOR RIVER, Figure 2 Boteti River Discharge at Rakops
40 The 2015/16 hydrological year has flows slightly similar to that of 2013/14 hydrological year, they 35 are currently the lowest flows experienced in the river ever since 2010/11. The flow is not expected 30 to rise anytime soon as we proceed with the new 25
hydrological year, because looking at the trend
from past years, when the hydrological year starts /s)
3 20 the flows tend to drop until May and eventually 2010/11 2011/12 start to rise again around April-May. The Boteti 15 2012/13
river has been experiencing low flows in the just 2013/2014 Discharge (m Discharge 2014/15 ended hydrological year to an extent that it dried 10 2015/16 up half way through the hydrological year around March, April to mid May. Unlike other major rivers 5
in the country, the Boteti river has a different
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when other rivers start to drop.
Latest update, 27th November-15.
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MAJOR RIVER, Figure 3 Figure 5: Water Levels for Chobe River at Mowana Lodge 7.00
The 2015/16 hydrological year has started, a normal to just below normal levels are 6.00 experienced at the moment. The water levels are expected to gradually rise until the end of 5.00 December, and beyond this point, significant
increase in levels are expected until the end of
May, and this will be as a result of inflow and 4.00 2010/11 rainfall water into Chobe river. The 2014/15 2011/12 hydrological year had experienced low levels in 3.00 2012/13 general as compared to the other past 2013/2014 2014/15
hydrological years, the levels never reached 4m metres in Levels Water 2.00 2015/2016 which is way far below the threshold (5.30m) Bankful Level where flood conditions start to develop and become a threat to human life. 1.00
Latest update, 27th-November-15.
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Date in days This report was prepared by the Department of Water Affairs, Botswana (Hydrology Division) For any enquiries please contact us at: 3607100/142/281/439.
Website: http:\\www.water.gov