Monitoring indicators
Putting IWRM principles in practice is a long-term process, which is aimed at making decisions at all management levels to ensure effective integration of water and other natural resource use factors into sustainable economic and social development. Meanwhile, IWRM is the cyclical process, efficiency of which is judged by indicators during monitoring, and which, if necessary, allows adjusting the action plan.
Indicators provide information in less detailed and more aggregated form rather than simply statistics. IWRM indicators must demonstrate the degree to which goals are achieved (such indicators are called as impact indicators) and progress (process indicators). This, in turn, demonstrates the completeness of achievement of IWRM goals and the effectiveness of the IWRM management system itself. This is proposed in the multipurpose water plans to a certain degree.
The factors of water availability, stability, uniformity, etc. are dimensionless. Multiplication of their values by 100 expresses the factors in %.
Water availability — degree of meeting the actual demand of given irrigated land area for water.
The situation is considered optimal (from the biological point of view) when a water availability factor equals to 1. In practice, a water availability factor does not always reflect an extent of water sufficiency for crops. Depending on purpose of the analysis, a water availability factor is calculated for different levels of water management hierarchy top-down, including the end users.
Depending on purpose of the analysis, a water availability factor is calculated:
- For an off-take or group of off-takes.
- Relative to plan and limit: actual/plan, actual/limit.
- For ten-day or a calculation period.
The group of off-takes, depending on composition and quantity of the off-takes receiving water from the canal, can be a farm, WUA, district, province, republic, command area of a balance site of the canal, the canal (system) command zone as a whole, etc.
The calculation period can be any time span: year, growing season, non-growing season, a part of growing or non-growing season.
In water distribution practice, the calculation is made on a cumulative total basis, i.e. the indicator is calculated for a time span since the first ten-day till the last ten-day of given calculation period.
Source: Manual on implementation of IWRM. Volume 2 Water management in irrigation systems
Stability factor
A diurnal stability factor (DSF) can be estimated for each off-take as follows
for a group of off-takes
A ten-day stability factor (TDSF) is calculated in the same manner for each intake structure (water diversion into an irrigation canal)
For a group of intake structures
The diurnal stability factor characterizes the degree of stability of flow rates during a day
- At intake point to irrigation canal (diurnal stability of head intake to irrigation canal).
- At points of lateral inflow to irrigation canal.
- At control gauging stations of irrigation canal.
- Of off-take (diurnal stability of water supply).
- Of a group of off-takes (farm, WUA, irrigation canal, etc.).
A maximum value of the stability factor is 1.
In practice, the stability factor like the uniformity factor has not been used yet since it is quite difficult to estimate it manually without computer aid and, most importantly, basically water users are more interested in stability and uniformity of water supply rather than water management organizations.
Source: Manual on implementation of IWRM. Volume 2 Water management in irrigation systems
Uniformity of water supply
A water supply uniformity factor is calculated for an off-take or a group of off-takes (farm, WUA, district, province, etc.)
Currently, a fundamental principle of water distribution coming from the principle of social equity is the proportionality. A water supply uniformity factor serves as a criterion of assessing social equity of actual water distribution among water users. A maximum value of water supply uniformity factor equals to 1. The higher the value of uniformity factor, the more equitable is the process of water distribution from the irrigation canal.
“From head to tail” uniformity factor. In the practice of water distribution, there is commonly the so-called “from head to tail” problem, when upstream users are supplied with irrigation water better than downstream users. A “from head to tail” uniformity factor shows the equity of water distribution along an irrigation canal.
Source: Manual on implementation of IWRM. Volume 2 Water management in irrigation systems
Efficiency factor (EF) of the irrigation network is the ratio of the amount of water delivered for irrigation to the amount of water diverted from the source to irrigation network.
Source: Manual on implementation of IWRM. Volume 2 Water management in irrigation systems
Land use factor (LUF) characterizes the ratio of irrigated (drained) cropped land area to the total area of irrigation system.
Water use productivity
Water productivity factor
Source: Manual on implementation of IWRM. Volume 2 Water management in irrigation systems
Land productivity levels and dynamics
Potential crop yield (PY) can be reached in highly fertile soil with optimal agronomic operations, ideal weather conditions and no yield losses through weeds, pests and diseases.
Actual climate yield (CY) is the maximum yield attainable in fertile soil under actual weather conditions (given the optimal agronomic operations).
Actual-possible crop yield (DVY) is the maximum yield, which can be reached in a field (taking into account its actual fertility) under conditions of a specific climatic year. It is assumed that DBY is attainable through optimal agronomic operations provided that all respective energy and labor inputs are made.
The routine method of estimation of the potential yield uses the coefficient of PAR (photoactive radiation). The formula is as follows:
where
PY is the potential yield of the main and sideline product on dry basis, center/ha;
q is unit caloricity of dry biomass, kcal/kg;
is total influx of PAR to the soil surface over the growing season, kcal/ha;
KPAR is coefficient of PAR, i.e. conversion from phytomass to yield, %.
Depending on quality of crops, the coefficient of PAR may vary, according to Nichiporovich, as: commonly observed – 0.5-1.5 %; good – 1.5-3.0 %; record – 3-5 %; theoretically possible – up to 8 %.
To get PY in main product units (e.g. grain or tuber) under standard moistness of biomass, the value of PY is multiplied by a special factor:
where
PYO is the potential yield of main product under standard moistness of biomass, center/ha;
B is the value of standard moistness of biomass in %;
α is the sum of parts in the ratio of the main product to the sideline product.
Crop yields largely depend on moisture content available for plants during growing. For potential productivity, the soil moisture must be within 60 to 100% of full field capacity during the growing season. Provision of plants with water is in the base of all agronomic operations. Lack of water accumulated in the soil often leads to reduced harvest.
The actual climate yield relative to moisture content is determined as:
where
YCY is the harvest of absolutely dry biomass, centner/ha;
W is the quantity of actually available moisture for plant, mm;
KW is a coefficient of total water consumption, m3/ha.
Productive moisture (W) is determined as the total moisture storage available for plants in a 1-m layer during sowing or restart of growing of winter crops and perennial grass plus effective rainfall in the growing season, i.e.
where
WO is the productive moisture storage in 1-m layer, mm;
OC is the quantity of rainfall in the growing season, mm.
Another method for calculation of CY, considering water and heat resources, is based on the use of a statistical relationship between harvest and hydrothermal indicator, which is estimated by Ryabtchikov’s formula:
where
HTP is a bio-hydrothermal potential of productivity, points;
W is the productive moisture storage, mm;
TV is growing season, ten-day period;
36 is the number of ten-days in a year;
R is a radiation balance or total PAR over the growing season of crop, kcal/cm2.
Each productivity point corresponds on average to 20 centner/ha of absolutely dry biomass yield and HTP is converted into yield by the following formula:
Then, the yield of absolutely dry biomass is converted into the yield of economic crop output under standard moistness.
The simplest way to calculate DVY achievable through natural soil fertility is to use the quality score attributed to land (or the so called bonitet of soil – Bs), which is taken from the respective scoring system:
where
CBS is the ‘crop’ price of the soil quality score: determined for concrete conditions of given territory through statistical analysis of the data on yields of each crop, kg/ha;
Êch is an adjustment factor for agrochemical soil properties.
A maximal decrease in quality score is related to unfavorable agrochemical soil properties: low content of labile phosphorus, exchangeable potassium, humus, excessive acidity, etc.