Updating the hydrology of the Baro-Akobo-Sobat basin

Transcription

1 Updating the hydrology of the Baro-Akobo-Sobat basin V Jonker (Aurecon), M Botha (Aurecon), S Crerar (BRL), A Mersha (ENTRO), JE Muso (ENTRO), F Negash, (ENTRO), N Sicard (BRL)

2 Background In 2015 ENTRO commissioned the Baro-Akobo-Sobat Multipurpose Water Resources Development Study Project Purpose: To promote socio-economic development, regional cooperation and peace through sub-basin wide cooperation in integrated water resources development and management Project team: BRL (lead), Aurecon & Yerer Project currently being completed

3 Project objectives To develop an Integrated Water Resources Management and Development Plan for the Baro-Akobo-Sobat Basin Based on a Strategic Social and Environmental Assessment (SSEA) - allows early/upstream identification/integration of environmental and social considerations into development of IWRMDP Main deliverables: Strategic Social and Environmental Assessment Integrated Water Resources Management & Development Plan Water resources model Spatial database Short term projects - Feasibility studies (x3) Medium and long-term projects TORs Feasibility studies (x3)

4 The Baro-Akobo-Sobat Basin Shared river basin Very little development Vulnerability to floods / droughts Environmentally sensitive areas Wetlands / marshes Forest ecosystems Antelope Migration Water dependent livelihoods Crop cultivation Pastoral farming Potential Hydropower Irrigation Tourism Lack of information Complex hydrology Conflicts natural resources

5 Physiography: Topography, Rivers, Sub-basins

6 Climate: Rainfall

7 Climate: Evaporation 399 masl 1740 masl 610 masl 421 masl Climate: Temperature

8 Climate: Droughts Droughts

9 Surface water modelling Data compilation and preparation Calibrate/Validate RR model Simulate long-term flow sequences Configure/Validate Systems model Scenario Simulations Model output to define Baseline and inform Scenario evaluation Objectives Quantify available water in space and time Assess hydrological and related social, environmental and economic impacts and benefits of interventions Refinements Subcatchment delineation Drainage network Review / Improve hydromet data Rainfall-Runoff modelling Floodplain dynamics Simulation period

10 Rainfall data Data sources NBI database of patched monthly rainfall values across Nile Basin ( ) Daily gridded rainfall - Swedish Meteorological and Hydrological Institute ( ) Monthly gridded rainfall - Climatic Research Unit Univ. East Anglia ( )

11 Rainfall data - chronogramme

12 Hydrological Data 83 gauging stations existed in the Baro-Akobo- Sobat Basin historically Data sources Nile Basin Encyclopedia Ethiopian Master Plan Reports Nile Basin Research programme Nile Basin Initiative ENTRO databases Ethiopian Ministry of Water, Irrigation and Electricity Previous studies

13 Flow data - chronogramme To be used for calibration Auxiliary Stations FLOW STATION NAME Alwero at Abobo Baro at Burebeiy Baro at Gambela Baro at Gambela Baro at Gambella Baro at Itang Baro at Kella Baro at Masha BirBir at Yubdo Geba at Suppi Pibor at Pibor Post Pibor at Pibor Post Pibor upstream of Khor Gila mouth Pibor upstream of Khor Gila mouth Sobat at its mouth into White Nile (at Hillet Doleib) Sobat at Nasser Sor at Metu Sor at Metu Abu Tong cut at its mouth into White Nile Adura at its head downstream of Baro-Adura bifurcation Adura downstream of Khor Makwai mouth Agwei at its mouth into Pibor Akobo at its mouth into Pibor Assua at its mouth into Bahr el Jebel Baro at its mouth into Sobat Baro downstream of Baro-Adura bifurcation Baro downstream of Baro-Adura junction Baro downstream of Khor Jakau mouth Baro downstream of Khor Machar head Baro downstream of Khor Makeir head Baro upstream of Baro-Adura bifurcation Baro upstream of Baro-Adura junction Baro upstream of Khor Jakau mouth Baro upstream of Khor Makwai head Khor 18 kms upstream of Machar head at head Khor 18.5 kms upstream of Machar head at head Khor 3.5 kms upstream of Machar head at head Khor 4.3 kms downstream of Machar head at head Khor 4.8 kms upstreamof Machar head at head Khor 6.5 kms upstream of Khor Jakau mouth at its head Khor Atar at its tail into White Nile Khor Barakwich at its mouth into Baro, 7 kms downstream of Machar head Khor Fullus at its mouth into Sobat Khor Geni at its mouth into Pibor Khor Gila at its mouth into Pibor Khor Jakau at its mouth into Baro Khor Lolle at its mouth into White Nile Khor Macap at its mouth into Pibor Khor Machar at its head (offtake from Baro) Khor Makeir at its head Khor Makwai at its mouth into Adura Khor Mokwai at its mouth into Pibor Khor Nyanding at its mouth into Sobat Khor Twalor at its mouth into Sobat Khor Wakau at its mouth into Sobat Pibor at its mouth into Sobat Pibor downstream of Akobo mouth Pibor downstream of Khor Gila mouth Pibor downstream of Khor Makwai mouth Pibor upstream of Akobo mouth Pibor upstream of Khor Makwai mouth Sobat at 2 kms downstream of Nyandig mouth Sobat at its head Sobat downstream of Khor Twalar mouth Sobat upstream of Khor Twalar mouth White Nile At Kosti White Nile at Malakal White Nile at Melut White Nile at Mogren (Khartoum) White Nile at Renk White Nile downstream of Jebel Aulia Dam White Nile downstream of Lake No White Nile upstream of Maya Berboi head White Nile upstream of Maya Sinyora Gauge CALENDER YEAR SOURCE EMP NBRP NBI NBRP EMP NBI NP NP NBI NBI NBE NBI NBE NBI NBE NBE EMP EMWE LEGEND All Months Data Availabl 6 Months Data Available 1 Months Data Available No Data Available

14 NAM Model calibration Baro Gambella Alwero Abobo Observed Simulated Difference Mean Annual Runoff % (million m 3 /a) Standard Deviation of % Monthly Flows (m 3 /s) R Observed Simulated Difference Mean Annual Runoff % (million m 3 /a) Standard Deviation of % Monthly Flows (m 3 /s) R

15 Model configuration and conceptualisation

16 African Wetlands GIEMS D15 GIEMS D3 TTI

17 Flood progression: Aug to Dec 2007 Flood progression - ADD

18 Floodplain/Wetlands: Maximum modelled inundation surface areas Machar Marshes Model validation - Floodplain seasonality and extent Sobat Veveno/ Lotilla/ Badigeru Gambella Plains Gwom/ Agwei Kangen Wetland Machar Marshes Max area (km2) Min area (km2) Avg. area (km2) Sobat Gambella plains Gwom / Agwei Badigeru /Veveno/ Lotilla Kangen

19 Model Validation - observed flows Baro River u/s Pibor confluence Sobat Hillet Doleib

20 Surface Water Baseline: Simulated stream flow ( )

21 Water Balance (Baseline) Outflow to White Nile: 13 BCM/a Total runoff generated: 26 BCM/a

22

23 Groundwater Yield

24 Sediment yield High Sediment Loads - Major issue Causes Erosion, Steep slopes, High intensity rainfall, Poor farming practices, Deforestation, Trampling (cattle)

25 Final scenario evaluation Scenario 1: Precautionary Principle - no encroachment into environmentally sensitive areas. Irrigation dam storage volumes reduced. All potential hydropower dams except Tams Dam and Birbir Dam. Scenario 2: An extension of the Precautionary Principle case, similar to Scenario 1, except that Tams Dam and Birbir Dam are included. Scenario 4a: Full-development case, with Tams Dam operated to maximise hydropower production. Scenario 4b: Full-development case, with Tams Dam operated to optimise irrigation and flood control. Scenario 3a: Compromise case, similar to Scenario 2, but with environmental water releases imposed on all dams. Scenario 3b: Compromise case, similar to Scenario 4a, but with environmental water releases imposed on all dams.

26 Defining the development space: Multidimensional analysis

27 Typical water resources model based outputs Seasonality of maximum wetland area - Machar Area (km ² ) Wetlands / Floodplains Month Scenario 0 Scenario 1 Scenario 2A Scenario 2B Scenario 3 Scenario 4 Water balance

28 Typical water resources model based outputs Large scale irrigation a Average Monthly Flow (BCM) Deficit Used Water 0.00 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month Flood risk Financial / Economic Water availability

29 Projects included in scenario analysis

30 Scenario evaluation: metrics

31 BAS IWRMDP

32 Thank you!