OPERATIONAL WATER RESOURES MANAGEMENT FRAMEWORK
6. CONCLUSIONS AND RECOMMENDATIONS
6.4. MODELLING AND DECISION SUPPORT SYSTEMS
To enable an organisation such as the ICMA to effectively implement operational water resources management with the sophisticated software systems and models implemented during the development of the AOWRMF, technical support and maintenance contracts with the software specialist were required. Without such contracts, many of the upgrades and improvements done to the modelling and decision support system required during this study would not have been feasible and they are thus recommended as an important aspect to include in an AOWRMF.
The inclusion of both planning and operations information in an integrated DSS has enabled the ICMA and its stakeholders to keep track of both the planning and operational aspects of IWRM (documented in section 1.2.1) and make informed decisions on OWRM that is cognisant of both these aspects. The automated real time acquisition, processing, management, dissemination and archiving of both the real time and historical data through this DSS has also provided great assistance to the staff of the ICMA in managing the large volumes of data input and output, which it is assumed would not have been possible without, given the small staff contingent of the relevant ICMA division (1 hydrologist and 1 manager). This automation in conjunction with the aforementioned support contracts enabled the successful management of these large data volumes with limited staff.
Further short term operations specific recommendations:
Any DSS and associated models should be installed on a proper network server with appropriate protocols and backup regimes in place to ensure reliability and sustainability of the DSS. This study quickly showed that the existing network, server and internet access at the ICMA was not sufficient to support the large data and information acquisition, processing, management, dissemination and archiving needs and these had to be upgraded before the AOWRMF could be fully developed.
Weather forecasts continue to be improved and these should be compared and included into the short term model to improve the flow forecasting of the models.
The CRMIB claim that fluctuations in weather conditions (such as temperature, wind, humidity and evaporation) from day to day significantly affect the flow in the lower portion of the Crocodile River during the low flow season (July to October). This claim has not been investigated. It is possible that an understanding of this correlation and the development of an indicator to monitor its influence could improve the short term flow forecasting and is recommended for investigation. Linked to this, an increase in the number of evaporation stations or the use of remotely sensed evaporation data is recommended.
Data assimilation, which updates predicted data with actual measured information from the installed real time river flow data loggers ensuring that forecasts are always using updated boundary conditions, is valuable in improving flow forecasts.
The current DHI NAM hydrological model performs suitably during the winter months, but fails to correctly simulate the summer hydrological pattern. This should be investigated further and recommendations on improvements made.
A calibration of the Mike 11 outputs conducted against observed flow by Greaves et al. (2009) showed that the volume differences between observed and simulated flows were large at certain gauges. Possible causes of this include poor water use data and poor rainfall runoff (NAM) model performance and should be investigated further.
Further long term planning specific recommendations:
The water use distributions patterns used in the long term model are static average distributions patterns based on allocated water use only. It might be beneficial to revisit the water use distribution patterns used in the model and replace them with near real time estimates of actual use and distribution patterns.
The use of serial correlation constraints in the stochastic generator of the planning model significantly reduces the uncertainty of flow (and storage) forecasts through the dry season.
Rivers that show strong serial correlation should consider incorporating these types of constraints in their planning models.
The antecedent conditions are taken into account through a stochastic methodology which looks at month on month correlations in a catchment. The inclusion of a rainfall based stochastic generation technique that could be put through a hydrological model would take into account antecedent conditions and improve results particularly in extending long term planning model projections to several years in advance. This technology is now available and could be investigated to improve modelling estimates.
Conclusions and recommendations specific to the implementation of the ecological flow requirements:
A new methodology to determine the ecological flow requirements on a weekly time step was pioneered through this study (Mallory, 2010), as existing methods entailed setting up real time hydrological models using real time rainfall data as input and which was not available at a sufficient level of accuracy. It has proven to be a great success and the outputs are accepted by the CROCOC stakeholders. That methodology is thus recommended as a suitable methodology for the calculation of the ecological flow requirements where good data on river flows and water use is available and insufficient data for rainfall is available. The development of the real time DSS to support the implementation of the ecological flow requirements and the establishment of the CROCOC to allow opportunities to discuss its implementation also created the environment in which the KNP and CRMIB have learnt to work together on this matter when they were previously unable to agree. The combination of the creation of this decision making environment, DSS and the pioneering methodology to calculate the ecological flow requirements were critical to the successful implementation of the AOWRMF.
However, some gaps and issues were identified during the study and should be rectified by the ICMA where possible:
The ecological flow determination model uses the “present day flow” ecological flow regime described in the DWA ecological reserve determination study and not the original C-class ecological reserve requirement stemming from that study. Although this is currently accepted by all stakeholders including DWA, the current ecological flow regime being implemented is only preliminary and is yet to be finalised through the DWA ecological reserve classification project that has recently commenced. This may result in a revised ecological flow requirement regime for implementation.
It is suspected that compliance with the ecological flow requirements may exhibit a significant correlation with the annual runoff. The methodology of Riddell et al. (2013) used to evaluate compliance with the ecological flow requirements does not factor in any possible influence of the annual runoff against the MAR. Although the presentation of the ecological flow requirements as percentage exceedance curves is deemed to factor this influence into account, it is still not fully understood whether the annual runoff has a significant influence on compliance or not. This should be investigated further to better remove the impacts of long term climate fluctuations on the evaluation.
The DWA X2H016 Tenbosch flow gauging site has shown significant fluctuation in flow between day and night. It is not understood how these sub-daily fluctuations may influence the river health. This should be investigated further.
The assumption that if the downstream ecological flow requirements were met at the DWA X2H016 Tenbosch flow gauging site only then the upstream sites would also be met may not always be correct and does not hold for tributaries. Further research is needed if the ecological flow requirements for the tributaries are to be implemented.
The implementation of the ecological flow requirements has been centred on the river flow quantity aspects in this study and compliance has thus only be measured in term of river flow quantity. The water quality related aspects are equally as important and must still be incorporated in the AOWRMF.