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Muluadwa

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Muluadwa last won the day on January 28 2011

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  1. hello GMS users, I wonder, how I can use GMS files to be used in Visual MODFLOW? How can I import/ export? Regards, Yohannes
  2. Hello GMS users Could there be options to simulate mining (dewatering) other than as a drain cell? such as Lak package, assigning high hydraulic conductivity/ storage value? Specific details of my area- The orebody is located 100-150 m below ground. The task is to simulate the drawdown and recovery of the groundwater in the vicinity of the mining area and to assess the impact of dewatering on surface water (river is found <150 m, represented using river package). It is a fracture flow system. 4 Hydrostratigraphy units, from upper to lower layer in order- oxidized layer, jointed layer, sheared zone orebody layer and basement layer. Time series recharge is estimated as rainfall %. K vaue was estimated from packer tests (1*10-6 m/s upper layer to 5*10-8 m/s for the basement). The principal aquifer is the jointed layer =4*10-7m/s. From previous mining within the model area located downgradient, the groundwater level has not been recovered for the last 15 years (since end of the mining). Could this indicate low storage value of the aquifers? poor recharge mechanism? Could this be a challenge to represent a discrete fracture flow system of the area as a porous media using MODFLOW? Other than a new mining site (which is located upgradient), the old mining (the one located at downgradient) is also planned to restart mining at the same time. Also, Could pilot point and regularization assist calibration (steady and transient) in fractured flow system? Suggestions, ideas, approach and sharing experiences are appreciated. Thanks Yohannes
  3. Hello MODFLOW users Could there be options to simulate mining (dewatering) other than as a drain cell? such as Lak package, assigning high hydraulic conductivity/ storage value? Specific details of my area- The orebody is located 100-150 m below ground. The task is to simulate the drawdown and recovery of the groundwater in the vicinity of the mining area and to assess the impact of dewatering on surface water (river is found <150 m, represented using river package). It is a fracture flow system. 4 Hydrostratigraphy units, from upper to lower layer in order- oxidized layer, jointed layer, sheared zone orebody layer and basement layer. Time series recharge is estimated as rainfall %. K vaue was estimated from packer tests (1*10-6 m/s upper layer to 5*10-8 m/s for the basement). The principal aquifer is the jointed layer =4*10-7m/s. From previous mining within the model area located downgradient, the groundwater level has not been recovered for the last 15 years (since end of the mining). Could this indicate low storage value of the aquifers? poor recharge mechanism? Could this be a challenge to represent a discrete fracture flow system of the area as a porous media using MODFLOW? Other than a new mining site (which is located upgradient), the old mining (the one located at downgradient) is also planned to restart mining at the same time. Also, Could pilot point and regularization assist calibration (steady and transient) in fractured flow system? I am using visual Modflow-PEST. Suggestions, ideas, approach and sharing experiences are appreciated. Thanks Yohannes
  4. Hello, Currently, i am asked by our client to predict a rate of dewatering required during construction of pump stations. Pump stations are proposed to be constructed at a depth of between 3.5 - 4.5 m below ground surface. In the proposed area the standing water level ranged from 0.4 m - 1.5 m below ground surface. K value ranges from 1.06 m/day to 1.93 m/day. Appreciated for any idea on how to estimate rate of dewatering (i.e to keep the water level below 3.5 to 4.5 m) using an analytical model that accounts for the range of conditions expected ( SWL and K ) at 4 pump stations. Regards Yohannes
  5. Hi everone, Currently, I am calibrating a seepage face and flow rate towards a quarry site using cross sectional model (2D). the model has been calibrated well against the measured flow rate and groundwater level from three observation bores along the section. I wonder if the ratio Kv/Kh ~ 500 is realistic. The aquifer is sandy gravel overain by sandy material. I would like to justify this ratio and see if there are case studies, documents relevant to the ratio of hydraulic conductivity ( vertical vesus horizontal). Could this be a none- uniqueness problem with model calibration. Regads Yohannes Melbourne, Australia
  6. Hi all', I would like to simulate the outflow rate out of a saturated compacted fill material 120 m by 60 m pit area (1.8 m depth) with 4 layers units (clay/gravel). Leakage is detected at the leachate extraction and detection sumps. The fill material- could be saturated during time of placement (since there was 160 mm of rainfall during this time). Therefore, there has been no recharge/rainfall since capped. It is well capsulated with clay liners (sidewall/ bottom of the pit)in place. The water table in the area is deep 12 m below surface. The task is to figure out if the outflow/leakage is coming out of the saturated fill material or it is leakage from surface (which is unacceptable). I am planning to simulate the outflow rate and match with the observed flow rate at the leachate extraction sump (coming out after 3 months since placement, this could be due to delayance effect?. Do we expect a constant outflow rate through out or varies exponentially with time? How long do we need to pump out if the leakage is coming out of the filled mataerial. How can I simulate this problem this using MODFLOW? regards Muluadwa
  7. Hi all', I would like to simulate the outflow rate out of a saturated compacted fill material 120 m by 60 m pit area (1.8 m depth) with 4 layers units (clay/gravel. Leakage is detected at the leachate extraction and detection sumps, at the bottom of the pit. The fill material- could be saturated during time of placement (since there was 160 mm of rainfall during this time). Therefore, there has been no recharge/rainfall since capped. It is well capsulated with clay liners (sidewall/ bottom of the pit)in place. The water table in the area is deep 12 m below surface. The task is to figure out if the outflow/leakage is coming out of the saturated fill material or it is leakage from surface (which is unacceptable). I am planning to simulate the outflow rate and match with the observed flow rate at the leachate extraction sump (coming out after 3 months since placement, this could be due to delayance effect?. Do we expect a constant outflow rate through out or varies exponentially with time? How long do we need to pump out if the leakage is coming out of the filled mataerial. How can I simulate this problem this using MODFLOW? Thanks Muluadwa
  8. am using two alternative models to simulate the quarry site: 1. I am planning to use high K value for the bottom layer instead of drain package to simulate the groundwater discharge to the quarry site ( at the bottom). However there is a contrast in K value (8640 m/day to 5 m/day). What K value do I need to put as an additional layer in between, to get rid of non-convergence problem. I presume even the average value of the two K (4320 m/day is much higher comparing with overlying aquifers)? 2. Is there any previous work or example for simulating pre-quarrying, quarrying and post-quarrying time? Basically post-quarrying refers to landfill and there will be no loss of evaporation from the quarry site. regards Yohannes Australia
  9. I am using two alternative models to simulate the quarry site: 1. I am planning to use high K value for the bottom layer instead of drain package to simulate the groundwater discharge to the quarry site ( at the bottom). However there is a contrast in K value (8640 m/day to 5 m/day). What K value do I need to put as an additional layer in between, to get rid of non-convergence problem. I presume even the average value of the two K (4320 m/day is much higher comparing with overlying aquifers)? 2. Is there any previous work or example for simulating pre-quarrying, quarrying and post-quarrying time? Basically post-quarrying refers to landfill and there will be no loss of evaporation from the quarry site. regards Yohannes Australia
  10. Currently I am modeling a quarry site proposed for a landfill (both at steady and transient). However the model failed to converge. About the model: 60 km2 area (150*150 m grid) refined at the quarry area (70*70 m). Drain cells have been placed in the quarry site (proposed landfill). As an alternative, I tried to use high K value for the cells at the bottom the quarry site to allow less resistant to groundwater inflow (and with constant head) but it did not converge either. Purpose of the model: 1. To simulate depression of groundwater elevation in the vicinity of a proposed landfill and impact on surrounding groundwater quality due to groundwater extraction from sumps beneath the landfill. 2. To simulate the impact of a leachate contamination from a neighboring landfill approximately 500 m from the proposed landfill. 3. To simulate the impact of leachate leakage from the proposed landfill if the liner was breached following the cessation of pumping. Any idea on how to fix the problem (stabilising and calibrating the model) is appreciated. Also I was wondering if there is a means to fix the instability problem using MODFLOW-SURFACT? regards, Yohannes Melbourne, Australia
  11. Currently I am modeling a quarry site proposed for a landfill (both at steady and transient). However the model failed to converge. About the model: 60 km2 area (150*150 m grid) refined at the quarry area (70*70 m). Drain cells have been placed in the quarry site (proposed landfill). As an alternative, I tried to use high K value for the cells at the bottom the quarry site to allow less resistant to groundwater inflow (and with constant head) but it did not converge either. Purpose of the model: 1. To simulate depression of groundwater elevation in the vicinity of a proposed landfill and impact on surrounding groundwater quality due to groundwater extraction from sumps beneath the landfill. 2. To simulate the impact of a leachate contamination from a neighboring landfill approximately 500 m from the proposed landfill. 3. To simulate the impact of leachate leakage from the proposed landfill if the liner was breached following the cessation of pumping. Any idea on how to fix the problem (stabilising and calibrating the model) is appreciated. Also I was wondering if there is a means to fix the instability problem using MODFLOW-SURFACT? regards, Yohannes Melbourne, Australia
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