Assessing Water Sharing Rules in Unregulated Rivers in NSW: Mooki River

Transcription

1 46th Annual Conference of the Australian Agricultural and Resource Economics Society Canberra, February 2002 Assessing Water Sharing Rules in Unregulated Rivers in NSW: Mooki River Aluwihare, P.B., Crean, J., Young, R.T Economic Services Unit, NSW Agriculture 1 The new Water Management Act (2000) requires water to be specifically allocated for environmental purposes to try to improve river health. Water sharing plans are being developed which establish extractive and environmental shares to river flows. A key consideration in the development of these plans is the economic trade-offs associated with different allocation options. In unregulated catchments, allocation rules typically involve significant restrictions to extractive access at times of low river flows, which also coincides with periods of environmental stress. The highly variable nature of stream flows in unregulated catchments creates challenges not only to the development of plausible sharing rules but also to the assessment of their effects. In this paper proposed water sharing rules in the Mooki sub-catchments in Northern NSW is examined. A combination of representative farm (linear programming) and hydrology simulation modelling is used to explore these effects. Key words: flow sharing rules, modelling, farm-level economic impacts. The views expressed in this paper are of the authors and not necessarily those of NSW Agriculture or the New South Wales Government

2 1 1. Introduction Water policy reform has received considerable attention in recent years. This is due to growing community concerns regarding environmental degradation in rivers and wetlands, increasing evidence of the poor state of land resources in irrigation areas and a greater government focus on improving the economic efficiency of water allocation. Significant reforms to regulated rivers (those where flows are regulated by major irrigation storages) and groundwater resources have been under way for several years (Crean and Young 2001). The NSW Government is now implementing a suite of reforms to the management of unregulated rivers. In unregulated rivers across New South Wales (NSW), the absence of an efficient set of rights governing access to water is one of the main factors contributing to a decline in river health and preventing an improvement in the efficiency of water use. The deterioration of stream health, decline in the condition of riparian vegetation, damage to the habitat of threatened species and a decline in water quality (increase in salinity, turbidity, and decline in dissolved oxygen) are the main environmental problems found in unregulated rivers (DLWC 2001a). These problems are caused mainly by the extraction of water during low and moderate flows. Natural low flows are important for maintaining pool connectivity, minimising stagnation and stratification of pools, and preventing concentration of pollutants (DLWC 2001a). Maintenance of pools during dry periods is also critical for the survival of fish and aquatic species. Excessive extraction of moderate flows affects the distribution of food and transportation of sediments, nutrients and organic carbon downstream. Moderate flows are also important for de-stratification of pools. In addition to improving environmental outcomes, improving economic efficiency and equity has emerged as a major issue in water management as competition for surface water has increased. However, the absence of a clear specification of water access rights has been a major barrier for the efficient management of water in the unregulated rivers of NSW.

3 2 The NSW government is currently addressing this poor specification of property rights through the development of a suite of water sharing plans for each unregulated river in the state. These are being developed by community based River Management Committees (RMCs) and detail the way water is to be shared between the environment, irrigators and other users. Twelve environmental objectives have been established as a basis for the development of water sharing plans (DLWC 2001b). These include the need to better mimic natural flow variability and protect low and moderate flows. While the economic benefits associated with these environmental improvements may be high, changing the flow access rules may also impose significant costs on existing irrigators. Therefore, in developing socially acceptable flow access rules the committees need to consider trade-offs between water for the environment and for other users. Natural resource management agencies, like NSW Agriculture, provide support to RMCs in developing their water sharing plans. This includes assistance in assessing the socio-economic trade-offs associated with various sets of river flow access rules. NSW Agriculture has provided a number of reports to RMCs evaluating trade-offs for regulated rivers and for groundwater aquifers (Carter et al. 2000; Jayasuriya and Crean 2000, 2001; Jayasuriya et al. 2001). However, the approaches developed for regulated rivers and groundwater cannot be directly applied for unregulated rivers. This is because of the highly variable nature of river flows, within and between years and the complicated rules regarding flow extraction and application to crops. In this paper a methodology developed to assess the on-farm impacts of flow rules for unregulated rivers in NSW is discussed. This is done by reference to a study undertaken for the Namoi Unregulated River Management Committee (NURMC) of the Mooki Catchment in northern NSW. The paper is structured as follows. Section 2 provides background information about the Mooki Catchment. Flow rules developed for the Mooki by the NURMC are outlined in Section 3. Section 4 contains a discussion of possible methodological approaches for assessing the impacts of water sharing rules in unregulated catchments

4 3 and the approach adopted in this study. Section 5 presents the results. Finally, a discussion and conclusion are presented in Section The Mooki Sub-Catchment The Mooki sub-catchment lies at the eastern end of the Namoi Valley located in Northern NSW (Figure 1). The Mooki sub-catchment covers an area of about 840 square kilometers which is about 2 per cent of the Namoi Catchment area. Irrigated agriculture is an important contributor to the regional economy of the Namoi Valley. The value of irrigated agricultural production was around 290 million dollars in 1997 (NSW Agriculture 2001a). The Mooki sub-catchment was settled by European graziers in the 1830s. Dryland cropping progressively expanded on the black alluvial soils of the flood plain during the first half of the last century. Irrigation development began in 1965 which also focused on the black alluvial soils of the flood plain. Currently there are 23 irrigators licensed to extract water from the Mooki River. About 50 percent of these have access to surface water only while the remainder has access to both surface and groundwater. The total area authorised for irrigation using surface water is around 3,500 ha. Currently, around 2,900 hectares have been developed for irrigation (Powell 2001). The irrigated agricultural enterprises in the Mooki sub-catchment include cotton, wheat, maize, summer oilseeds and vegetables. Over the past two decades, the area of cotton has expanded rapidly reflecting its relative profitability. Cotton and wheat account for around 70 and 20 per cent of the irrigated area, respectively. Back to back cotton and a cotton-wheat rotations are the most common practices in the catchment. Furrow irrigation is the predominant irrigation method for all crops, although there is some spray irrigation in the upper sub-catchment. Most irrigated farms also have a dryland farming component. Sorghum and wheat are the most commonly grown dryland crops in the catchment.

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6 MLs Assessing water sharing rules in unregulated rivers River flows The Mooki River is dependent on inflows from the Phillip, Warrah and Quirindi water sources as well as localised rainfall in the Mooki sub-catchment. The Mooki River displays a highly variable flow pattern. The daily pattern of flow for a typical year is detailed in Figure 2. While the median daily flow is 10 MLs, it ranges from 0 to over 50,000 MLs. Due to the highly variable flow pattern and the small number of days on which flow is available for extraction (around 35 percent of the time) on-farm water storages are essential for ensuring irrigation availability throughout the irrigation season. Figure 2. Daily flow in the Mooki River, Note: The daily flows during days 291 to 351 have been truncated in order to present a reasonable scale for other flow events. Actual daily flows reached maximum of 4,500 MLs Day

7 6 3. Rules for Sharing River Flows 3.1 Current Flow Sharing Rules Currently, irrigation licences are based on the area irrigated irrespective of the volume of water used. A Commence to Pump (CTP) threshold establishes the minimum flow level that the river must reach before irrigators can start their pumps. This rule aims to protect low flows and allow flow to build up to levels useful for irrigators in down stream river reaches. In the Mooki sub- catchment one CTP level has been set at 50 MLs/day. 3.2 Proposed Flow Sharing Rules Under the Water Management Act 2000, all area based licences are being converted to a volumetric basis to better define irrigators access rights, to encourage improved irrigation efficiency and to facilitate trade. Volumetric entitlements have been established by looking at the historical area of each crop type irrigated for each irrigator. These areas were then multiplied by the theoretical water requirement for each crop type for that climatic zone (different climatic zones were established across the state). In addition to an annual volume limit, flow variability requires a mechanism by which each flow event can be shared between irrigators, the environment and others users. A generic approach has been developed across the state to divide river flows into four categories. These are based on a flow duration curve (Figure 3) and are defined as follows: 1. Basic low flows - very low flows not available for extraction. As a general rule flows exceed this level for 95 percent of days (the 95 th percentile). 2. Class A - low flows generally between the 95 th and 80 th percentile. 3. Class B - low to moderate flows generally between the 80 th and 50 th percentile.

8 Megalitres per day Assessing water sharing rules in unregulated rivers 7 4. Class C - moderate to high flows, freshes and floods. Refers to flows generally between the 50 th and 0 percentile (flows exceed this level less than 50 per cent of the days). Irrigators are permitted to extract a proportion of flows in each flow class. The proportion is determined for each river and is usually based on historical extraction levels. The volume of water allowed for extraction by irrigators determined by this method is called the Bulk Extraction Volume (BEV). Water management committees in unregulated rivers have been determining the daily share of water between extractive users and the environment through establishment of BEVs for different flow classes. In the case of the Mooki River, A and B class flows do not exist due to the highly ephemeral nature of the stream (Powell, 2001). Given the high demand for river flows, Class C flows have been further divided into three sub-classes (C1, C2 and C3). Three flow sharing options were proposed by the Namoi Unregulated River Management Committee (NURMC) for sharing river flows within these classes (see Powell, 2001) which are summarised in Table 1. Figure3. Flow duration curve for the Mooki River Class C Basic low flows % of time flow is exceeded Class B Class A Source: DLWC (2001a)

9 8 The current rules represent the base case against which the proposed flow sharing options are compared. Under the base case, irrigators could access all river flows above the CTP level (50 MLs/day). In practice irrigators only extract a proportion of flows because of limits on pump and on-farm storage capacities. There is effectively no BEV currently in place. Table 1. Proposed flow sharing options in the Mooki Flows class Flow level MLs/day Bulk Extraction Volume (MLs) Option 2A Option 2B Option 3 CTP 100 Nil Nil Nil C , C 2 1,000 3,000 1,500 1, C 3 > 3,000 2,100 2,100 2,100 The flow sharing Options (2A, 2B, and 3) provided in Table 1 impose varying levels of restriction on the amount of water which can be extracted by irrigators within C1 and C2 classes. Access to C3 class flows is constant across all flow sharing options. The BEV is distributed among individual irrigators in proportion to their licensed entitlement but is restricted by physical ability to extract water. Individual flow extraction will continue to depend on pump capacity and the size of on-farm storage. Some additional rostering arrangements may be established by irrigators to ensure equitable access to the resource given the differing location of individual farms along the river. Currently, no rostering rules are practiced with upstream irrigators getting first access to each flow. In the absence of any existing rostering arrangement, some assumptions were made about how water was shared among individuals. These are outlined in section 4.

10 9 4. Methodology 4.1 Overview Water policy reforms generally involve some form of modification of property rights involving a re-allocation of resources. Resource re-allocation decisions are commonly assessed in a benefit-cost framework. The economic efficiency of different allocation policies can be assessed by comparing the social benefits and costs associated with each policy. Underpinning the benefit-cost framework the potential Pareto improvement criterion states that resource re-allocation decisions are efficient if those who are made better off can compensate those who are made worse off and still be in a better situation. Of course, for the criterion to be satisfied it is not necessary for compensation to be actually paid. There are, however, a number of difficulties associated with adopting the standard benefit cost analysis framework when considering issues that are likely to yield environmental benefits, like increased water allocations to the environment. The major difficulty relates to the appropriate valuation of environmental benefits (particularly those in the non-use category) so that they can be incorporated into a benefit-cost framework. To overcome some of the conceptual arguments regarding valuation, a variation on the standard benefit cost framework can be adopted through the use of an opportunity cost or threshold value approach. The threshold value approach avoids the need to directly place monetary values on environmental goods. The approach is based upon estimating the opportunity costs which would be the consequence of a particular resource decision. The opportunity costs are then directly compared to the environmental outcomes (quantified in non monetary terms) which are expected from the proposal. The impacts on irrigated agriculture of water reforms can be analysed at two levels. The first at a broader regional scale, and second at a more disaggregated catchment or farm level. The latter approach is adopted in this study. There is a range of techniques available for assessing farm level impacts of water policy reforms. These techniques range from simple budgeting methods to optimisation methods. However, the

11 10 selection of the method depends ultimately on the purpose of the analysis and the nature of the problem being addressed. The community based approach to the implementation of water reforms provides the overall context for farm level analyses undertaken by NSW Agriculture. The purpose of quantitative work within this context is to facilitate social choice. More specifically, it is to provide information to help RMCs understand how the farm level financial impacts of water sharing options are distributed so that appropriate tradeoffs can be made. The central role that RMCs have in the process and their broad community representation (with varying levels of understanding of economics) suggests that relatively straightforward methodological approaches should be used. Methodological approaches should meet simplicity and transparency requirements whilst also remaining sufficiently rigorous to capture real effects. The types of problems proposed by RMCs commonly involve some form of restriction to the access of water resources. The significance of these restrictions will depend on climatic conditions that influence both the availability of river flow for extraction and water demand. When climatic variability is likely to influence the relative effects of water management options, then more stochastic methodologies are required (eg. simulation). NSW Agriculture has adopted various representative farm modelling methods to analyse the on-farm impacts of re-allocation of water in NSW catchments. Cater et al. (2000) adopted a simple whole farm budgeting method to estimate benefits or farm returns for analysing the on-farm impacts of groundwater re-allocation rules in the Namoi Valley. However, in estimating net farm returns this method elicited farmer response to changed water availability directly from the farmers concerned. Many of these responses were found to be irrational, designed more to influence policy outcomes of the study, rather than accurately reflecting rational farmer behaviour. As such they did not optimise resource allocation or minimise risk. Modelling at a catchment and farm level is a widely used approach analysing problems in agriculture and water resource management (Crean et al. 2001). Catchment level modelling considers differentiated agriculture demand sites (agricultural production zones or nodes) where each agricultural demand site can be

12 11 modelled as a single farm. Farm scale modelling is done by selecting a representative farm or farms depending on the variability of farm characteristics in the catchment. NSW Agriculture has adopted farm scale modelling to evaluate the on-farm impacts of environmental flow rules in regulated river catchments in NSW (Jayasuriya and Crean 2000; Jayasuriya et al. 2001). However, these models cannot be applied directly to unregulated rivers because they use total seasonal water availability instead of weekly or daily water availability. In addition, the reliance on on-farm storages by irrigators on unregulated rivers further complicates the modelling of water balance and irrigator behaviour. Modelling of irrigation on unregulated rivers therefore needs to consider the dynamic nature of water management within the economic model The Approach This study adopted a combination of hydrology simulation and linear programming (LP) to evaluate alternative flow sharing options in the Mooki sub-catchment. The principle reason for adopting a simulation approach was to consider the variability of impacts due to the nature of stream flows and climatic conditions. Historical rainfall and stream flow data indicate that the Mooki sub-catchment is a highly variable system (see Figure 2). This suggests that using a deterministic or average year analysis would not adequately represent the farm level impacts of different flow sharing options because changes in river flow availability directly impact on the area of irrigated crops and hence farm returns. It is assumed that farmers respond to reductions in water availability by changing their crop mix to make the best use of available water and convert part of the area laid out for irrigation to dryland production. The income from this area will be estimated by the gross margin for an equivalent area of dryland crop. The model assumes that daily BEV is perfectly shared by all irrigators. The approach is shown schematically in Figure 4. The hydrology simulation and farm level optimisation models are discussed in the following sections.

13 12 Figure 4. Schematic of the modelling approach Flow rules Sacramento Hydrology Model Generate stream flow data for 88 years Individual daily flow shares Farm level Optimisation Model 4.2. Stream flow simulation model (Sacramento model) The Sacramento model was used by DLWC to simulate stream flows. It is a continuous rainfall-runoff model that generates stream flows from rainfall and evaporation records. The principle of the model is that it uses soil moisture accounting to simulate the water balance within the catchment Farm level optimisation model A single representative farm was used in the analysis to represent all irrigators who have access to surface water entitlements. This was done for two reasons. First, because the homogeneous nature of farming systems in the sub-catchment. Cater et al. (2000) undertook a GIS analysis of farm size and various attributes, such as irrigation entitlement and on-farm storage size and found that these attributes to be relatively homogeneous. Key features of the representative farm were based on information derived from earlier irrigation surveys and advice from local irrigators and advisory staff. The main characteristics of the representative farm are provided in Table 2. Overhead costs for the representative farm were derived from a survey conducted of 22 irrigators in the Mooki and Cox's Creek catchments for an MDBC project by Bennett and Bray (2001).

14 13 Some of the key economic data used in the economic model are discussed below: Gross margins gross margins of crops used in the model were obtained from the Farm Enterprise Budgets for Northern NSW (NSW Agriculture 2001b). Gross margins are estimated in year 2000 prices. Overhead costs for the representative farm include costs such as wages for permanent labour, administration costs, capital depreciation, etc. Cost of water includes pumping costs and water charges. Table 2. Key features of the representative farm. Key physical characteristics Total farm size (Ha) 442 Surface irrigated area (Ha) 162 Dry land area (Ha) 280 On-farm storage size (MLs) 729 Pump capacity MLs/day 125 Surface water entitlement (ML) 1,294 Irrigated crop mix (%) Irrigated Wheat 25% Irrigated Cotton 61% Irrigated Maize 14% Dry land crop mix (%) Wheat 50% Sorghum 50% Farm overhead costs $75,500 The objective function of the farm level optimisation model is to maximise total annual net farm income, Z, which is given by, Max Z Subject to: n. i ci Ai K n i 1 a ij Ai L j

15 14 Where: Z is annual total net farm income, c is gross margin per unit area of land for crop i, A is area cultivated under crop i, K is the total annual overhead cost for the farm, a is the amount of resource j used per unit of crop i, L is the maximum availability of resource j. Net farm income is a measure of farm profit and measures the return to the operator for their labour and management and return to all capital investment on the farm. The model considered number of resource constraints. Constraints on production resources were monthly water availability and annual water entitlement and land laid out for irrigation and dryland area. The other constraints were specific crop constraints, pump capacity, and on-farm storage capacity. A capital constraint is embedded in the specific crop constraints. A cotton-wheat crop rotation was specified given it is the most commonly practiced crop rotation in the area. Monthly flow availability for extraction was estimated by aggregating the daily extractable flow. Daily extractable flow was estimated by proportionally allocating daily BEV based on annual entitlement (pro rata basis). The model assumes all river water is routed through the on-farm storage before being applied to crops. This irrigation flow path requires a series of equations to represent the water availability constraint. These include an on-farm storage water balance equation and an on-farm storage capacity constraint. On-farm storage water balance The on-farm storage water balance is governed by the on-farm storage continuity equation. The linear equation representing the continuity equation is as follows: S t S W t 1 t 1 et

16 15 Where: S t is the amount of water stored in time t, I t is the amount of water pumped into storage in time t, W t-1 e t is the amount of water released from the storage for irrigation in time t-1, is the storage losses in time t (evaporation and seepage). The storage capacity constraint is as follows S t C Where, C is the capacity of the on-farm storage. Estimation of crop demand (gross irrigation demand) was an important part of estimating the model coefficients needed to determine monthly storage release. The following equation was used to estimate monthly irrigation requirements. IR = ET c ERF RSM + PI GIR = IR * IE Where, IR is the irrigation requirement at root zone, ET c is the crop evapo-transpiration, ERF is the effective rainfall, RSM is the residual soil moisture at the time of planting, PI is the pre-irrigation requirement. GIR is the gross irrigation requirement (ex on-farm storage), IE is the irrigation efficiency (conveyance and application). Since data was not available, residual soil moisture and pre-irrigation requirements were not considered in the estimation. Crop ET (ET c ) values were estimated by NSW Agriculture s Water Use Efficiency Unit using the Penmann and Monteith method were used in estimating crop water requirements (NSW Agriculture 2001c). Effective rainfall for each crop was estimated using monthly rainfall multiplied by crop effectiveness factors. Gross irrigation requirement was estimated at 70 per cent

17 16 irrigation efficiency. Since the estimated GIR is a theoretical one, a factor (0.3 ) was used to scale it down to represent more realistic irrigation requirements. The scaling factor was determined by comparing the estimated GIR and irrigator reported GIR. The irrigators generally under irrigate by 30 per cent compared to theoretical crop water requirements (NSW Agriculture 2001b). This under irrigation is reflected in the yields used in the analysis. 5. Results 5.1. Impact on average net farm income The financial impacts of flow sharing options using the farm level modelling approach are provided in Table 3. From the results it can be seen that the introduction of Options 2A, 2B and 3 are expected to result in a decrease in net farm income of 5.0%, 5.1% and 5.9%, respectively. All three Options will have statistically significant impact on irrigators. While there was no statistically significant difference in impacts between Options 2A and 2B, the restriction in access to C2 class flows under Option 3 reduce farm performance to a greater degree. Table 3. Summary of impacts using the representative farm model with river flow data Whole Farm Gross Margin (WFMG) - Average ($) - Standard deviation ($) Net Farm Income (NFI) - Average ($) - Standard deviation ($) Current Rule Rule 2A Rule 2B Rule 3 278, , , ,396 17,737 28,935 29,020 30, , , , ,896 17,737 28,935 29,020 30,196 Impact on WFGM % Impact on NFI % T-test results( Comparing means against the mean of current rule), at 5%

18 Decrease in Net Farm Income ($) Assessing water sharing rules in unregulated rivers Distribution of impacts across years Figure 5 illustrates the impacts of flow sharing options across the 88-year simulation period. This shows that impacts are higher in dry years. However, the incidence of impacts is complicated by the operation of the on-farm storage (OFS), the timing of river flows and the subsequent effect of the flow sharing rules on BEV's. Consequently, impacts occur only in a proportion of dry years. The non-normal distribution of impacts of flow sharing options is reflection of the non-normal river flow pattern. Standard statistic theory suggests that, under a non-normal distribution, a comparison of means may only lead to false conclusions. Analysis of the distribution of impacts of different water sharing options was therefore undertaken using cumulative probability distribution function (CDF) as suggested by Anderson et al. (1977). Figure 6 provides a summary of results in the form of cumulative distribution functions (CDFs). This shows that for around 70 percent of the years, Option 2A, 2B and 3 are expected to reduce farm incomes by 0-4%. For around 20 per cent of time incomes may fall by 5-22%, and for around 10 per cent of years they are expected to fall by between 23-51%. Figure 5. Impact of flow sharing options, % 50% Option 2A Option 2B Option 3 40% 30% 20% 10% 0% Year

19 Probability Assessing water sharing rules in unregulated rivers 18 Figure6. Cumulative probability distribution of impacts, Option 2A Option 2B Option Analysis of variability - 70% of years Options 2A/2B/3 reduce farm incomes by 0-4% - 20% of years Options 2A/2B/3 reduce farm incomes by 5-22% -10% of years Options 2A/2B /3 reduce farm income by 23-51% % 5% 10% 15% 20% 25% 30% 35% 40% 45% 50% 55% Decrease in Net Farm Income (%) 6. Discussion and Conclusions The focus of this study was to develop a methodology capable of evaluating flow rules for unregulated river catchments. The paper is based on a study undertaken on behalf of the Namoi Unregulated River Management Committee to analyse the onfarm impacts of three proposed flow options for the Mooki sub-catchment. The major task of this study was to develop a method capable of accommodating the ephemeral nature of river flows and the opportunistic water management practices adopted by irrigators in unregulated rivers. The study used a combination of hydrology simulation and LP optimisation modelling techniques to develop a farm scale model to estimate the impacts of flow rules. The Sacramento model was mainly used to simulate natural river flows for 88 years. Linear programming was subsequently used to construct the economic model. The LP model was able to incorporate the dynamic nature of irrigation flow management,

20 19 where irrigators need to optimise flow extraction and on-farm storage to maximise farm returns. The model was successful in predicting impacts in different flow and climatic years and was therefore seen as helpful in assessing the impacts of flow options developed by the NURMC. The model can also be used to predict optimal on-farm storage capacities for different annual volumetric flow extraction limits. This can be done by varying the on-farm storage capacity for a given annual flow extraction limit (entitlement). This output can then be incorporated in a cost benefit analysis to identify optimal storage capacity. As with many models this model also makes a number of simplifying assumptions. The assumption of the flow path from river to on-farm storage to crop is not the only way of irrigation practiced in unregulated rivers. For example, irrigators may irrigate by directly pumping water from the river onto crops. When this occurs, this model may underestimate net farm income, thereby over estimating the impacts of changes in flow rules. The other assumption of this model is that it models irrigation monthly irrigation rather than more frequently as would be practiced by irrigators. This assumption also tends to under estimate the magnitude of impacts.

21 20 References Anderson, J. R., Dillon, J. L., and Hardaker, B.J., 1977, Agricultural Decision Analysis, Iowa State University, Iowa. Bennett, R. L and Bray, S., 2001, Summary of responses to Murray Darling Basin Commission (MDBC) Project No , Irrigation Futures Framework Modelling, Breeza Plains Farmer Survey, NSW Agriculture, Gunnedah. Carter, A., Crean, J. and Young, R. 2000, Impacts of Ground Water Re-allocation options in the Namoi Valley, NSW Agriculture, Orange. Crean, J. and Young, R., 2001, Modelling the farm level implications of water reforms in NSW, Australia, invited to ACIAR water policy workshop, Bangkok, June. Crean, J., Jayasuriya, R. and Jones, R., 2001, Regional agricultural implications of environmental flows in the Murrumbidgee Valley, Australia, invited paper to ACIAR water policy workshop, Bangkok, June. DLWC, 2001a, Water Sharing Plans for the Unregulated Phillip, Mooki, Quirindi and Warrah, Department of Land and Water Conservation, Tamworth. DLWC, 2001b, Advice to Water Management Committees, No 6, Water extraction volumes and daily flow shares in unregulated rivers, Department of Land and Water Conservation, Sydney. Jayasuriya, R., Crean, J., 2000, The on-farm impacts of ground water management scenarios in the lower Murrambidgee, NSW Agriculture, Orange. Jayasuriya, R., Crean, J., 2001, The on-farm impacts of environmental flow rules in the Lachlan Valley, NSW Agriculture, Orange.

22 21 Jayasuriya, R., Crean, J. and Hanna, R., 2001, Economic assessment of water charges in Lachlan Valley, NSW Agriculture, Orange. NSW Agriculture, 2001a, The Draft Namoi Catchment Irrigation Profile, Water Use Efficiency and Advisory Unit, NSW Agriculture, Dubbo NSW Agriculture, 2001b, Farm Enterprise Budgets, NSW Agriculture, Tamworth. NSW Agriculture and Department of land and Water Conservation, 2001c, Volumetric Conversion of Irrigation Licences on Unregulated Rivers: Theoretical Determination of Annual Volumetric Entitlements, NSW Agriculture, Dubbo. Powell, S., 2001, The Draft Interim Flow Access Rules: Mooki sub-catchment. A report to the Namoi Unregulated River Management Committee, DLWC, Tamworth.