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Smith_GH Reports 1970s

The purpose of the study was to source and evaluate all existing groundwater data within the Tshiping WUA, delineate important groundwater management units (GMUs, also called GRUs) and identify gaps in existing data so as to optimise the future Tshiping hydrocensus survey.

Following the completion of Phase A of the Tshiping Water Users Association (WUA) study on regional groundwater information and groundwater status assessment, Phase B was approved. The purpose of Phase B is to evaluate and implement the data collected in Phase A and determine initial surface water and groundwater balances and status assessments for the catchment and groundwater management unit (GMU) areas to feed into a Desktop Reserve determination.  Click below to download the document.

Executive Summary

Introduction

A regional groundwater study was initiated in 2015 to determine the historical development, present status to identify management and planning requirements in quaternary catchments D41J and D73A in the Northern Cape Province. The Tshiping jurisdiction boundary covers an area of 873 272 ha with 334 farms. The development of mining in the area since the 1950’s and large scale dewatering since 1976 within a rural agricultural area characterised mainly by livestock and wildlife farming with irrigation and vegetation changes puts pressure on groundwater as a resource.

The objective is to determine the historical groundwater quantity baseline/s to serve as a reference against which current impacts and status can be measured and develop a management plan to ensure sustainable management of groundwater as a sole resource of water in this semi-arid and drought prone region.

Tshiping Water Resource Information Management System (TWRIMS)

A critical part of the project was to develop a Water Resource Information & Management System (WRIMS) with regional data on rainfall, surface water and groundwater that serves as a single and official water data reference. The online information system (www.tshiping.digitalzoo.dev) is open for access to all interested and affected parties and used to progressively increase the understanding of the hydrological system and dynamics to enable sustainable management of water resources in the WUA. It is one of the largest local groundwater data sets in the country, with 112 rainfall stations, 4828 boreholes of which 3805 (79%) have water level measurements and 82 (1.7%) have abstraction rates and all available technical reports dating back to 1938. Rainfall data is available since 1920 and some water levels date back to 1905.

Study methodology

The bulk of the study focuses on a macro analysis of the regional groundwater trends over long periods of time with some analyses done on a more local scale where required e.g. the Gamagara Channel, Dolomite and Lava Aquifers. The data was analysed using statistical methods to provide significance of assurance intervals that can be reproduced.

A total of 19 groundwater management units (GMUs) were identified based on the hydrogeology and drainage. The study area covers a surface area of 8743 km2 with GMUs that range from 8000 ha to 872 000 ha.

Rainfall

An analysis of the rainfall since 1920, showed that there was no change in mean annual precipitation over time, with long term mass plots indicating straight line trends. The MAP appears to increase as one moves east in quaternary catchment D41J (377 mm/a), and decrease as one moves south into quaternary catchment D73A (326 mm/a). The area is drought prone with prolonged dry cycles interrupted by flood events. The records show typical wet and dry cycles of two to three years, however, a deviation from the norm occurred between 1963 and 1986 where two lengthy dry cycles, 7 years and 10 years occurred on either side of a 7 year long wet cycle. The extreme wet period and floods in 1974 was an anomaly that lasted from 1973-1976 during which the annual precipitation ranged from 400 mm/a, to 1000 mm/a. Wet (flood) conditions (>600 mm/a) occurred in cycles of 11 to 30 years in 1955, 1963, 1974, 1988, 2001, and 2017.

The average monthly rainfall is 29 mm/month with a standard deviation of 43 mm/month indicating a very high variability. Monthly rainfall that generates runoff must typically be >75 mm/month which occurs only 20% of the time while significant runoff occurs when rainfall exceeds 100-150 mm/month which occurs only 7% of the time.

Hydrogeology

Regionally, there are two main types of aquifers. The first is the basal and major Ghaap Plateau Dolomite (and banded iron formation) Aquifers that arguably forms the largest groundwater resources in the country. Borehole yields range from 5-100 ℓ/s with recharge rates in excess of 5% of rainfall. Other minor fractured aquifers either overlie or straddle the dolomite that are formed by localised Kalahari Formation and fractured/weathered quartzite, shale and lava formations where borehole yields are low at 0.2- 1.0 ℓ/s and recharge rates of less than 0.5% of rainfall. Some of these can be classified as non-aquifers with no defined sustainable yield or recharge while along linear regional fault/dyke structures exceptionally high borehole yields of 5-10 ℓ/s can be found but which reduces in yield with time.

Baseline conditions: Historical Springs

The occurrences of historical regional springs was analysed in an area of 30-60 km around the Tshiping Water Users Association boundary that were spatially mapped prior to 1973 as part of the 1:50 000 topographic map series and by Smit (1977). The spatial distribution of known springs reduced by at least 95% since 1968/1972. Of the 191 historical springs recorded prior to 1974, there are only 9 known springs that either flow constantly or intermittently during/after wet periods.

The flow rates of the dolomitic springs on the Ghaap Plateau were monitored by the Department of Water & Sanitation since 1959. There were 7 large dolomitic springs known as “eyes” in the 1960’s of which only 3, namely the Kuruman A Eye, Great Koning Eye and Manyeding B Eye are still flowing today. The Kuruman A Eye, which is the largest natural spring in the southern hemisphere, provides the best historical account of groundwater in the region. The flow from this spring was at 0.5 million m3/month in the period from 1968-1972, which increased by more than 5 fold to 2.7 million m3/month post the 1974 flood and took until 2003 (29 years) for the flow to decay to the same flow as prior to 1974. The 1988 flood event, although smaller than the 1974 event prolonged the elevated flow conditions of the Kuruman A Eye. The latest reliable flow records from the Kuruman A Eye was in 2013 with a flow rate of 0.35 million m3/month, which represents a reduction of 46% of the pre 1974 flood flow conditions and an 87% reduction in the post 1974 flow rate. The spring flows over time shows that significant recharge only takes place in extreme wet months where rainfall exceeds 100-150 mm/month.

The major reduction in spatial occurrences of springs and flows of the Dolomitic Spring Eyes can be explained by two factors which is either increased abstraction or reduced effective recharge. The Kuruman A Eye Compartment is well studied and although there is some borehole abstraction, there is no suitable soil for significant irrigation. It is estimated that the borehole abstraction is less than 10% of the spring flow. This means that the only logical conclusion is that effective recharge reduced over time.

Research indicates that bush encroachment has the potential to reduce effective recharge significantly, especially in semi-arid regions.

Baseline conditions: Historical water levels and trends

The reduction in spatial occurrences in springs correlates with a regional reduction in groundwater levels and borehole yields in the reference or background environment not influenced by mining dewatering and not taking historical shallow wells into account, as these skew the data. There is more than one and at least 3 historical baselines as follows:

  1. Trend 0: Pre-1950 baseline with average water level depths at 7 m. The deepest levels were at D41J-G7A (Lava) at 39.6 m and the shallowest at 16.8 m in D41J-G5 (Lava). Truter et al (1938) references average water levels of 32.1 m for D41J-G7A (Lava).
  2. Trend 1: 1951-1972 or Pre-1974 baseline with average water level depths at 0 m. The deepest levels were at D73A-08 (Lava & Kalahari) at 47.7 m and the shallowest at 2.4 m in D41J-G7G (Gamagara).
  3. Trend 2 (1973-1979): The baseline water levels were elevated significantly regionally to 5.0 m depth due to extreme wet conditions.

The spatial distribution of water level depths from Smit (1977) with data collected from 1968 to 1972 could be used to generate a contour map of baseline water levels in D41J-G7A, G2, G3, G4, G5 and G6, which is an important reference for baseline water levels pre-1974.

Trend 1 to Trend 2 (1973-1979): There was a regional average rise by 16.1 m to 5.0 m during and after the 1974 floods (Trend 2, 1973-1979). The baseline was elevated significantly during this extreme wet cycle. The shallowest water levels were in D41J-G7G (Gamagara at 2.4 m) and D41J-G5 (Lava at 3.6 m).

Trends 2 to 7 (1979 to 2018) water levels declined on average by 11.5 m from a mean of 5.0 m in 1979 to the current level of 16.2 m (-0.27 m/a). The decline in water levels was observed in 60% boreholes while there was still a rise of ±40% in Trend 6 (44%) & 7 (39%) (2004-2018). There is a comparative trend between the historical spring flow recession and decline in regional water levels.

Trends 7 vs 1 2018 compared to 1972  shows that for the non-mining GMUs the average water levels is 5 m above the pre-1974 baseline and 11.5 m higher than the pre-1950 baseline levels for the non-mining GMUs. The largest differences are in D41J-G5 (Lava) which is -6.03 m and D41J-G7A that is -3.47 m below the 1972 baseline levels. Water levels in D41J-G7G (Gamagara) are 3.12 m higher than the 1972 baseline levels. In D73A-08 the water level data shows that it is 30.6 m higher than the 1972 baseline which is large and inferred to be due to abstraction in 1972.

Trend 7 (2010 to 2018) shallow water levels: The known water level data that indicate the distribution of shallow water levels (<20 m) shows that water levels <5-10 m co-exist with deeper water levels with specific reference to D41J-G7G (Gamagara), D41J-G6 (Sishen), D41J-G7A (Lava), D73A-08 (Lava & Quartzite) and D73A-06 (Kolomela & Beeshoek). Most of the known shallow water levels occur in D41J-G7G (Gamagara) and D41J-G6 (Sishen). The fact that the shallow and deep water levels occur close together in some areas testifies to hydrogeological compartments that are formed horizontally and vertically within and across GMUs.

Trend 7 (2010 to 2018) deep water levels: The distribution of deep water levels (20->50m) occurs in D41J-G6 (Sishen), D41J-G7A (Lava), D41J-G3 (Kathu), D73A-06 (Kolomela & Beeshoek), D73-C01 (Quartzite) and C92-C01 (Finsch), which is due to mining dewatering and pumping of farming boreholes.

Baseline conditions: Historical borehole yields

Historical borehole yields: Three historical sources that reference measured borehole yields, (Truter et al, 1938, Enslin, 1939 and Smit, 1970(1977)). The average borehole yield in the Ongeluk Lavas was low at 1.1 ℓ/s with no recorded yields > 5 ℓ/s. The average yield of the superficial deposits (Kalahari beds) was lower at 0.85 ℓ/s. There are some zones along regional dykes that did have high yields in excess of 5 ℓ/s, but was the exception with less than 2% of boreholes expected to have these high yields. New data was acquired from work done by Enslin (1939) on the quartzite formations mainly west of Olifantshoek and Smit (1977 with data collected from 1968-1972) that contained large data sets on Kalahari, Lava, Dolomite and other aquifers up to the Molopo River that still has to be analysed and compared with current data.

Baseline conditions: Water quality

Regional groundwater quality data was collected by Smit (1977) and by Verhagen et al, (1979) that provides valuable baseline groundwater quality data sets that can be compared to data from today in the same hydrogeological units. Smit collected groundwater quality data sets in the Kalahar, Lava, Quartzite and Dolomite Aquifers.  An initial screening assessment indicated that there are significant differences in water quality in the pre-1974 (Trend1) vs the post-1974 (Trend 2) data sets with specific reference to chloride values that concentrated and water quality that deteriorated in the Kalahari and Lava Formations since the 1974 flood event. The water quality data can be used to estimate groundwater recharge rates.

Mining dewatering impact assessment

Mining dewatering is an obvious concern that would reduce groundwater levels and was a specific focus of the study.  However no pattern could be found outside the defined impacted zone at Sishen Mine as spatially, springs disappeared across and beyond the study area and not only close to mining areas. The Macarthy Spring which is located on the southern (dyke) boundary of the Sishen Mine Main Compartment Aquifer and 15.3 km south of the Sishen Mine boundary, is one of the very few that still flows at an estimated 1.5-2.0 ℓ/s, which is higher than the flow rate measured by Smit prior to 1973 when it was flowing at 0.3 ℓ/s.

Mining dewatering occurs in the Major Dolomite and Banded Iron Formation Aquifers and has a high impact within defined impact zones that is formally delineated in the case of the Sishen Mine but not in the case of any of the other mines, which is a gap in the groundwater data. The Sishen Mine currently abstracts groundwater at 15 million m3/a, and Kolomela Mine at 10 million m3/a, which collectively equates to 62% of the yield of the Hartebeespoort Dam. Excess water from these major resources is supplied to the Sedibeng Vaal-Gamara Pipeline that feeds to communities, mines and farms in the Kalahari that forms part of the basic human need reserve.

There is no determinable pattern or correlation in terms of the (i) depth to water level or (ii) the rate of decline with distance from the edge of the boundary of the dewatering impacted zone in D41-JG6 (Sishen). The depth to water level and rate of decline/rise was analysed for zones of 2.5 km, 5 km and 10 km from the impacted zone edge. Data from 109 boreholes shows that the depth to water level is 21.6 m and the rate of water level decline changes to a rise of +0.08 m/a in a zone 2.5 km outside the impacted zone edge, which then decline again at -0.29 m/a with a depth to water level of 21.8 m in the zone 5-10 km outside the impacted zone edge. There are deep water levels (>40 m) and high rates of decline (>-0.9 m/a) that occurs far away (+10 km) from the impacted area edge that cannot be linked to mining.

The findings from the water level analyses are independently supported by a chemical mixing model based on chloride, which revealed that the findings above is independently supported by a chemical mixing model based on chloride, which revealed that The resultant leakage from the Kalahari + Lava Aquitards both on and adjacent to the compartment is calculated from the chemical mixing model results in 2.5% of the dewatering from 2008 or 11.6 ℓ/s, which increased to 2.9 % from 2014 – 2017 or 13.3 ℓ/s or an increase of 25.8 m3/d/a, which is not representative of significant regional flow. The chemical mixing model however represents a maximum leakage due to the low background chloride values from 1979 and the fact that it cannot distinguish between the on- and off-compartment Lava & Kalahari leakages volumes.

Recharge and land cover (vegetation)

Recharge is a very important but complex aspect in the study area. If the maximum estimated farm water use cited by local farmers of 10 ℓ/ha/d (0.36 mm/a) is compared to a regional recharge rate of at least 2.5% (8.5 mm/a; it indicates that there must be a problem with recharge as the required farm water use rate of 0.36 mm/a represents only 0.1% of recharge, 20 times less than expected. Evidence of significant recharge is evident from the major floods that occurred in 1974 and 1988 that were typically >600 mm/a, with monthly rainfall of >100 mm/month. Recharge from smaller flood events (20-40 mm/month) is only effective in the Dolomitic Aquifers. The monthly rainfall that produces recharge therefore only occurs 25% of the time. Significant recharge in the non-dolomitic aquifers is produced by monthly rainfall of >100 mm/month which occurs only 7 % of the time. The recharge problem is also evident from the regional reduction in spring occurrences and flow reduction in dolomitic springs.

Water level logger data taken from 2014-2018 shows that rain events below 50 mm/month produced no recharge in 3 boreholes located in the Lava & Kalahari Formations (DE-08, SW751, BH8). The lava boreholes’ water levels rose by only 0.75-1.41 m during January – February 2017 when the cumulative rainfall was 403 mm, which represents recharge of 0.25% and 0.35% of rainfall which is insignificant. This type of monthly flood/wet event occurs only 0.5% of the time, which indicates that there is no significant recharge in the Lava & Kalahari Formations. During the same event, the water level in a dolomitic borehole (MAC 4) rose by 13 m representing at least 15% recharge of rainfall, which is significant and indicative of a major aquifer.

A plausible explanation for the reduction in effective recharge is land use and vegetation cover. There are several published research studies that proved bush encroachment in combination with soil cover does have a regional negative impact on the soil water balance in the study area and on reduction of both surface water and groundwater resources in the Northern Cape. If it is conservatively assumed that bush encroachment uses 300 mm/a more than the natural vegetation, then an equivalent of 5000 ha or 1.3 % infestation on the study area would match the 15 million m3/a, abstraction from Sishen Mine.

Since there is no major abstraction or any evidence of irrigation in the Kuruman Eye Compartment, the only plausible explanation of the reduction in flow which is currently flowing at only 60% of the pre-1974 flow rate, is a reduction in natural recharge. Based on the information available, there is evidence of bush encroachment in the Northern Cape and locally in the Kuruman Compartment. If the phenomenon of (i) the regional 95% reduction in spatial occurrences of springs, (ii) the reduction in cumulative dolomitic spring flows of almost 80% with no spatial pattern that can be explained, then a reduction in regional natural recharge is the only common factor. The negative impacts of bush encroachment is well researched and proven in Namibia (Colin Christian and Associates, 2010), Botswana (Ward, 2005), South Africa (Dzikitia et al, 2012, Calder and Dye 2001, Gibson and Low, 2003), the Northern Cape (Van Den Berg, 2010) and in the D41J catchment (Verhagen, et.al, 1979).

An observation is that the bushy vegetation infestation occurs preferentially in low lying areas (i.e. gulley’s) where surface water runoff would concentrate or pond, which are the groundwater recharge areas. Although this aspect needs to be further investigated, a reduction in historical effective recharge and an increase in borehole water abstraction provide the only plausible regional explanation of a reduction in groundwater levels and yields.

To verify the importance of vegetation on recharge, recommendations were made to install automated water level loggers on adjacent farms with visible bush infestation that are located next to farms where bush infestation is controlled.

Monitoring requirements

The gathering of sufficient groundwater data and monitoring is key to the understanding of the groundwater systems and sustainable management of the resources. Important recommendations were made to install a suite of automated water level loggers that can make daily measurements. These loggers are critical to the understanding of the groundwater status and system responses to abstraction and rainfall-recharge. Annual hydrocensus surveys are required on at least 100 selected boreholes to determine the changes in water quality during wet and dry cycles and how it influences recharge.

Groundwater balances (Reserve)

The regional water balance (GYMR) assessments indicated that the total minimum expected recharge for average rainfall conditions is in the order of 40 million m3/a. This reduces to around 6 million m3/a, in 1:20 year drought conditions. To put this into perspective, the yield of the Hartebeespoort Dam is 40 million m3/a. The natural recharge in the study area should be adequate to irrigate 4000 ha. The biggest user of water is mining that abstracts 40 million m3/a. It is estimated that at least 50% of the abstraction originates from aquifer storage in the major dolomitic aquifers.

The total actual abstraction of 47 million m3/a, exceeds recharge with a stress level of just over 120%. This means that there is an overall deficit of around 8 million m3/a in average rainfall conditions, which changes to a deficit of -41 million m3/a under 1:20 year drought conditions. Both D41J and D73A are over-allocated in terms of lawful water use. The allocations of 83 million m3/a, which is 35 million m3/a more than the average annual recharge and does not make provision for drought conditions with a stress index level of +200%. Not all GMUs are stressed as D41J-0G1-4 and D73A-01 to D73A-03, D73A-07 and D73A-09 & D71B-01 & D73B-01 and D73C-01 performs with stress levels below 25% even in drought conditions.

Conclusions

The gathering of sufficient groundwater data and monitoring is key to the understanding of the groundwater systems and sustainable management of the resources. Based on the data, the study found that there were four major factors that influenced the groundwater status (i) the 1974 major flood that elevated regional groundwater levels and spring flows significantly, (ii) mine dewatering at Sishen Mine that increased significantly since 1976, (iii) the advent of motorised pumps and Eskom Power in the late 1970’s, early 1980’s that made irrigation possible and (iv) the proliferation of bush encroachment triggered by the 1974 flood that is inferred to have a significant negative impact on effective groundwater recharge.

The trend in water levels represents changes in groundwater pressure head and the springs provides independent information on regional groundwater flow rates. As expected, these two variables are corresponding. An important aspect of the study was to determine the historical baseline reference spring occurrences with flows and the groundwater levels to determine macro trends that can explain the present day observations.

There are at least 3 historical baseline conditions determined by Trends. In Trend 0, the pre-1950 baseline with average water level depths at 26.7 m. The deepest levels were at D41J-G7A (Lava) at 39.6 m and the shallowest at 16.8 m in D41J-G5 (Lava). In Trend 1, 1951-1972 or pre-1974 baseline with average water level has depths at 21.0 m. The deepest levels were at D73A-08 (Lava & Kalahari) at 47.7 m and the shallowest at 2.4 m in D41J-G7G (Gamagara). In Trend 2 (1973-1979), the effects of the 1974 and 1988 flood events resulted in a major regional rise of water levels of 16.1 m and increased cumulative spring flows of 2.5 times the pre-1974 flows from of 0.83 million m3/month in 1960 to 2.12 million m3/month post-1974. Following the 1974 floods, water levels decreased continuously by an average of 11.5 m 1979 to the current level of 16.2 m (-0.27 m/a) while the cumulative dolomitic spring flows are correlated with a corresponding decline of almost 80% to 0.41 million m3/month in 2013. From 1972 to 2018, the regional occurrences in springs reduced by 95%, which corresponds with both the regional decline in water levels of -0.27 m/a, and the almost 80% reduction in dolomitic spring eye flows.

Water level logger data showed that there is no evidence of significant recharge in the Lava and Kalahari Formations based on data from 3 boreholes that either showed no or very low recharge rates of <0.35% of rainfall during significant rainfall events of 403 mm that occurred during January to February 2017 and represents an event with 0.5% (1:200) probability. This can be explained by a regional increase in bush encroachment that can have a significant negative impact on groundwater recharge and for which there is evidence in the study area and beyond.

Mining dewatering is the biggest user of groundwater. Impacts on water levels and yields are evident within a defined impacted zone in D41J-G6 (Sishen) with no evidence of dewatering impacts based on data from 140 boreholes in Trends 6 & 7 (2004-2018 located outside the determined impacted zone edge. The findings from the water level analysis is independently supported by a chemical mixing model based on chloride revealed that the resultant leakage calculated from the chemical mixing model results in 2.52% of the dewatering from 2008 or 11.6 ℓ/s, which increased to 2.9 % post 2014 or 13.3 ℓ/s or almost 25 m3/d/annum, which is not representative of significant regional flow. The mining impacted zones in D73A-06 (Kolomela) and C92-C01 (Finsch & Lime Acres) have not been officially determined, which is a gap in the study that should be addressed in follow up phases.

Recommendations

The study identified important recommendations of which the most important are listed below:

  1. Regional hydrocensus on selected boreholes to verify the water level and hydrochemistry distribution in the background or reference environment.
  2. This macro analysis was done based on the available data sets. Several localised gaps were identified in the spatial coverage of monitoring boreholes that requires monitoring boreholes fitted with automated loggers. The data from these new monitoring boreholes should be used to verify the findings of this analysis on a spatial and local scale. There are 34 existing loggers and an additional 98 new positions.
  3. The chemical mixing model to verify the mine water compartment leakage at D41J-G6 (Sishen) must be updated and analysed in more detail with isotopes as it provides results that are specific to leakage quantification.
  4. Update the historical baseline conditions with borehole yields and water quality that can be compared to the statistical analyses from Smit (1977) with data collected from 1968 to 1972. Additional water quality data is available from 1979 (Verhagen et al) and subsequently from 2003 that can be used to evaluate recharge trends based on water quality information.
  5. Investigate the historical and current land cover and status of bush encroachment using remote sensing
  6. Investigate the rainfall-recharge responses of regional automated logger data in detail.
  7. The mining impacted zones in D73A (Kolomela, Finsch, Sedibeng and Lime Acres) must be determined and quantified.
  8. The socio-economic value and impact of and on groundwater should be determined.

Lava farms: Experiences and groundwater use volumes

Groundwater is the only reliable resource for water supply in the area of the Tshiping Water Users Association (TWUA), which extends mostly within the boundaries of surface water catchments D41J & D73A in the Northern Cape Province. The TWUA was formed as a legal entity under the National Water Act (Act 36 of 1998) to manage the water resources in its jurisdiction area. A Water Resource.  Concerns raised by farmers that groundwater levels and yields are declining on the Ongeluk Lava Formations. The farms where most of the concerns were raised are located in surface water .

Following from the findings of Phases 2.1 (Lava focus study) and Phase B2B, specific conclusions were made regarding the status of land use, recharge, boreholes and groundwater abstraction and the regional groundwater situation in the TWUA study area. One of the main questions and concerns that the land owners have is why the water levels and availability is declining over time. The findings of Phases B2B supported the general concerns and it is important to note that based on current information, groundwater levels are declining in some areas, which means that there may not be water available in the medium to long-term future. Although some of the main concerns were identified and qualified with specific reference to recharge and land cover, abstraction of boreholes and mining dewatering, additional information is required in areas and aspects where gaps were identified.


A catchment management strategy that focuses on future development, water conservation and water management should have high priority. Although some significant indicators were identified, this aspect can only be confirmed if automated water level recorders are installed in specific areas and depths as recommended in the Phase B2B report. It will be important to review and optimize the exact number and locations of these recorders and positions.

Artesium Consulting Services (Pty) Ltd (ACS) was appointed by Tshiping Water Users Association (WUA) to review the ground water level data collected within the groundwater management units under which they manage. The Nineteen Tshiping WUA GMUs considered in this study include: D41J-G1 – G5, D41J- G7, C92C-01, D71B-01, D73A-01 -09, D73B-01 and D73C-01 (Table 1, Figure 1). The Sishen compartment (D41-G6) is excluded from this analysis as it has been analyzed in detail in the previous Phase B2B (Vivier, 2018). In this report, the hydrogeology of each GMU is overviewed.The key water users and receptors are identified, and the available borehole database and water level baseline levels and trends are analysed between 2015 (extreme dry) to 2022 (extreme wet) with specific reference to the reaction of water levels measured via loggers to evaluate recharge.