Regional Training Workshop on Integrating Groundwater Management withi - PDF document

1 Regional Training Workshop on Integratin
Regional Training Workshop on Integrating Groundwater Management within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya Groundwater – Surface Water Interactions. Regional Training Workshop on Integrating Groundwater Management within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya • Groundwater and Surface Water Interact continuously through the hydrologic cycle. • The hyporheic zone (stream bed) is the zone of most interaction. • Flows occur fro

2 m surface water (streams, lakes etc.) to
m surface water (streams, lakes etc.) to groundwater and vice - versa depending on the hydraulic gradient. • Interactions occur not only as water volume fluxes but also as chemical and water quality fluxes. • The direction , location and rate of these fluxes changes with time and season. They may also be influenced by anthropogenic activities such as pumping, drainage or impoundment. • Water resources management includes understanding both the nature, direction, location,

3 timing and volume of these fluxes. •
timing and volume of these fluxes. • A sound understanding of surface water – groundwater interactions lies at the core of catchment water management and optimum conjunctive use of the water resources. Groundwater – Surface Water Interactions. Regional Training Workshop on Integrating Groundwater Management within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya Key Differences between Surface Water Flows and Groundwater Flows. • Location: • Surface fl

4 ows occur in specific locations, streams
ows occur in specific locations, streams and lakes, principally controlled by topography. • Groundwater flows tend to be distributed broadly through the sub - surface. Topography is less important than formation hydraulic conductivity and hydraulic gradient . • Duration: • Surface water flows are of short duration, usually a few weeks to a few months. • Groundwater flows take place over years, decades and millenia . • Velocity: • Surface flows are rapid, of the scale of

5 meters / sec. • Groundwater flows ar
meters / sec. • Groundwater flows are slow, on the scale of meters / year or less. • Evaporation: • Surface water is subject to high evaporation losses • Groundwater is largely protected from evaporation losses • Quality: • Surface water is vulnerable to bacteriological contaminants and surface pollution. • Groundwater is protected from pollution but may be mineralized due to rock - water interactions. Regional Training Workshop on Integrating Groundwater Management w

6 ithin River Basins, 15 - 18 January 2019
ithin River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya Groundwater flow • GW in continuous slow movement from recharge areas (usually upland areas) to discharge areas (springs, baseflow, wetlands and coastal zones) • Natural flow through an aquifer is usually at low velocities (e.g. 1 m/day is high!) • The rate of flow and hence the turn - over time for groundwater is orders of magnitude slower than for surface water and hence groundwater requires a different mana

7 gement paradigm. Regional Training Work
gement paradigm. Regional Training Workshop on Integrating Groundwater Management within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya Baseflow is the groundwater component of stream flow. It varies depending on the climate, permeability of the basin and the topography amongst other factors. Regional Training Workshop on Integrating Groundwater Management within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya Interactions between surface water

8 and groundwater Regional Training Wor
and groundwater Regional Training Workshop on Integrating Groundwater Management within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya • Streams gain water from inflow of groundwater through the riverbed • Streams lose water to groundwater by outflow through the riverbed • There can be a seasonal and spatial variation in whether a stream is gaining or losing Regional Training Workshop on Integrating Groundwater Management within River Basins, 15 - 18 January 201

9 9, RCGW, KEWI, Nairobi, K enya Regional
9, RCGW, KEWI, Nairobi, K enya Regional Training Workshop on Integrating Groundwater Management within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya Regional Training Workshop on Integrating Groundwater Management within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya The effects of pumping on groundwater – surface water fluxes. Initially the groundwater feeds the stream, but in the last image, the flows are from the stream to the groundwater sy

10 stem. Regional Training Workshop on Int
stem. Regional Training Workshop on Integrating Groundwater Management within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya Groundwater interact with wetlands Similar to streams and lakes, wetlands can receive groundwater inflow, recharge groundwater, or do both: • Wetlands that occupy depressions in the land surface have interactions similar to lakes and rivers • Wetlands can be present on slopes; water table may intersect land surface, causing groundwater dis

11 charge, which permits the growth of wet
charge, which permits the growth of wetland plants • Riverside wetlands receive groundwater discharge, they have especially complex hydrological interactions and are subject to periodic water level changes Regional Training Workshop on Integrating Groundwater Management within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya Reduction of groundwater discharge to springs and stream base – may affect groundwater – dependent ecosystems, e . g . wetlands due to str

12 ess or loss of resilience from inadequat
ess or loss of resilience from inadequate water sources . Groundwater Quantity: Over - exploitation ...lowering of groundwater table may affect minor wetlands Regional Training Workshop on Integrating Groundwater Management within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya Some Consequences of GW abstraction Excessive pumping When pumping is further increased Normal consequences of any groundwater pumping Regional Training Workshop on Integrating Groundwater M

13 anagement within River Basins, 15 - 18 J
anagement within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya Source: GW - MATE Groundwater Quantity : Over - exploitation … .. Salinization Regional Training Workshop on Integrating Groundwater Management within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya Historic data When groundwater management starts to be implemented Monitoring data Baseline data (reference) Regional Training Workshop on Integrating Groundwater Management within River Ba

14 sins, 15 - 18 January 2019, RCGW, KEWI,
sins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya Management Challenges Regional Training Workshop on Integrating Groundwater Management within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya GWM in Practice • Identify critical points • Excessive drawdown with wells drying up • Water quality deterioration such that it is unsuitable for original use • Conflict between abstractors / users • Uncontrolled waste dumping • Decline of groundwater dependent

15 ecosystems • Reduced baseflow • De
ecosystems • Reduced baseflow • Declining springflow Regional Training Workshop on Integrating Groundwater Management within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya Direct groundwater - surface interactions. Groundwater use from shallow unconfined aquifers • Groundwater use from shallow unconfined aquifers, delays the timing and reduces the amount of surface run - off in the rainy season and decreases baseflow in the dry season. • Such baseflow may be

16 of critical importance especially durin
of critical importance especially during the periods of low flow and in semi - arid climates. • Baseflow provides provide perennial water to groundwater dependent ecosystems and the communities that survive from these resources Pollution/contamination transfer between the two resources • Interaction between surface water and groundwater can cause pollution to be transferred from one to the other. • Groundwater pollution can more persistent for centuries thereby reducing water

17 resources availability for generations
resources availability for generations to come. Regional Training Workshop on Integrating Groundwater Management within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya Direct groundwater - surface interactions. Groundwater recharge is impacted by surface water use. ✓ Damming rivers and abstracting water reduces downstream flow for indirect groundwater recharge through riverbed infiltration. ✓ This is often the major component of groundwater recharge in arid and

18 semi - arid environments. ✓ Irrigati
semi - arid environments. ✓ Irrigation excess and wastewater discharge (assumme regulated/permitted discharge) are also sources of groundwater recharge. Regional Training Workshop on Integrating Groundwater Management within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya Examples of opportunities for conjunctive management • Groundwater holds large volumes of water in storage, while surface water storage is moderate or small and often ephemeral. ✓ A conjunc

19 tive management strategy could suggest t
tive management strategy could suggest to allocate surface water resources before they run off or evaporate. (value of evaporation?). ✓ In contrast groundwater use can be increased in the dry season to offset the shortfall from surface water. ✓ Groundwater resources can provide a buffer in times of drought and water scarcity Regional Training Workshop on Integrating Groundwater Management within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya Examples of opportun

20 ities for conjunctive management • Man
ities for conjunctive management • Managed aquifer recharge (MAR) ✓ Can be done in identified suitable aquifers with surplus surface water during the wet season if there is excess flow. ✓ Recharging aquifers in this way will not only provide additional dry season water resources but will also allow for natural purification of any bacterial contamination in the surface water during infiltration. • Groundwater may be developed where demand is dispersed and moderate, while deve

21 lopment of surface water may focus on la
lopment of surface water may focus on large - scale demand and irrigation development. Regional Training Workshop on Integrating Groundwater Management within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya Examples of opportunities for conjunctive management • Balance upstream and downstream interests - demand and supply as influenced the interactions and connectivity between the surface and groundwater resources ( surface flow transfers downstream are rapid ) •

22 Financing of groundwater development and
Financing of groundwater development and monitoring is a key area for flexibility. ✓ In many instances, private and individual development of the resource takes place, particularly if the basin authority establishes a positive enabling environment such as, for example, subsidies for electricity or borehole drilling. • Water resources, water managers are able to better balance the different competing needs in the catchment through integration of the entire suite of available wa

23 ter sources. Regional Training Workshop
ter sources. Regional Training Workshop on Integrating Groundwater Management within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya Exercise Regional Training Workshop on Integrating Groundwater Management within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya EXERCISE Purpose: To share experience of groundwater quantity problems. Activity: Break into your groups Each group to (in 1 hour): a) Identify a common groundwater quantity problem in your co

24 untry . b) Discuss the nature and scale
untry . b) Discuss the nature and scale of the problem – is it anthropogenic or natural? c) How is the problem being managed, and who is responsible for the management? d) What have been the aims of the management and how successful has it been? e) What would you change to improve management of the problem? Regional Training Workshop on Integrating Groundwater Management within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya End Regional Training Workshop on Integrating

25 Groundwater Management within River Bas
Groundwater Management within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya Issues The hidden drought 300 m Regional Training Workshop on Integrating Groundwater Management within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya Issues The groundwater quality time - bomb Regional Training Workshop on Integrating Groundwater Management within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya Why is Groundwater Management needed? • Man

26 agement and protection of groundwater ha
agement and protection of groundwater has been seriously neglected, potentially endangering the resource. • The sustainability of groundwater is linked to policy issues influencing water and land use, and represents one of the major global challenges in natural resource management. • There is a need to integrate groundwater and surface water management to ensure better overall water management and allocation. Regional Training Workshop on Integrating Groundwater Management withi

27 n River Basins, 15 - 18 January 2019, RC
n River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya Salinisation (or intrusion of saline waters) – another widespread impact of excessive groundwater over - pumping . Groundwater Quantity : Over - exploitation ➢ occurs due to up - coning of saline water and mixing with fresh water, giving rise to an aquifer salinisation. ➢ a major problem for many coastal cities in some world’s river basins. Regional Training Workshop on Integrating Groundwater Management wit

28 hin River Basins, 15 - 18 January 2019,
hin River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya EXERCISE Title: Water Quality Management Issue: Mining impact on water quality in the West Rand: Calculation and interpretation The West Rand area of Johannesburg is one of the largest gold producing regions in South Africa . The area is underlain by quartzites and dolomites . Some of the mines are closed in 1908 ’s and since 2002 acidic mine water is decanting into the environment . Local farmers depend on the dol

29 omitic aquifer for water supply . The di
omitic aquifer for water supply . The discharge of toxic - rich effluent from gold mines and the proximity of slimes dams, tailings and rock dumps can also cause chemical and biological damage to aquatic ecosystems through flooding, clogging, altering streams and wetlands and deposition of radioactive and toxic metals within the drainage of the karst system . The run - off from slimes dams enters the drainage network that feeds into the surface water, karst system and groundwater . Regio

30 nal Training Workshop on Integrating Gro
nal Training Workshop on Integrating Groundwater Management within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya EXERCISE CONT During the mining process, rocks which are situated far below the surface are brought to the surface, where they are crushed and processed . Gold is extracted through chemical processing and the barren material is stored in slimes dams . The crushing and chemical processing expose and mobilize pyrite (FeS 2 ), a natural sulphur - rich component

31 of the rock that is then exposed to the
of the rock that is then exposed to the atmosphere and water . The oxidized sulphates in combination with water and bacterial breakdown produce sulphuric acid that in turn reacts with the rocks and soils to release and mobilize the metals . The acids and metals which are released are found in the rivers and groundwater that is contaminated by the runoff from slimes dams, tailings, rock dumps and mine effluent . Regional Training Workshop on Integrating Groundwater Management within Rive

32 r Basins, 15 - 18 January 2019, RCGW, KE
r Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya Task Acid mine decant flows downstream into dolomitic terrain in the West Rand . Discharge measurement was undertaken at six stations in two different months (February and August) . February is a rainy month, while August is dry . Station P 1 exclusively contains acid mine decant and the measured values change downstream . Calculate the seepage rate/amount of acid mine water into dolomitic aquifer . Give possible reasons for the

33 loss, the impact and increase at some s
loss, the impact and increase at some stations . Recommend mitigation measures . Regional Training Workshop on Integrating Groundwater Management within River Basins, 15 - 18 January 2019, RCGW, KEWI, Nairobi, K enya Acid mine decant in the West Rand, Johannesburg Discha rge Februar y August Seepage in Feb Seepage in Aug Q (m 3 /s) P1 2.214 1.075 Q (m 3 /s) P2 1.2177 0.7 Q (m 3 /s) P3 1.014 0.588 Q (m 3 /s) P4 0.3 0.28 Q (m 3 /s) P5 0.9 0.3 Q (m 3 /s) P6 0.45 0.207 Total m 3 /s