SIMULATION OF IRRIGATION WATER CONSUMPTION IN
THE YELLOW RIVER BASIN USING A DISTRIBUTED
HYDROLOGICAL MODEL
Chong LI1, Dawen YANG2, 3, Guangheng NI3and Heping HU3
China Institute of Water Resources and Hydropower Research, Beijing
2
Department of Civil Engineering, University of Tokyo
3
Department of Hydraulic Engineering, Tsinghua University
1
With an increasing pressure of population growth, agricultural irrigations in the Yellow
River basin have been greatly expanded during the last 30-years in particular. Irrigation
management is the first step to a wise management of water resources in the Yellow
River basin. Using a 20-year (1981-2000) forcing data, irrigation water consumption is
estimated using a grid-based distributed hydrological model. The spatial and temporal
distribution of irrigation water consumptions is explored. Attempt of simulating irrigation
shows potential applicability of the model on water resources management.
INTRODUCTION
The Yellow River, also called Huanghe in Chinese, is the second longest (also the second
largest) river in China. The Yellow River flows about 5,500 km distance in the main
course and accumulates 753,000 km2 of drainage area (Fig. 1). It has about 100 million
population and 1200 million ha farmlands in which near half are irrigated by the Yellow
River. The main irrigation districts are located in the northern part (Inner Mongolia), in
the tributaries of midstream (Fenhe basin and Weihe basin) and on both sides along the
lower reaches (Fig. 1). The water shortage problem has become more and more serious
with the vast amount of irrigation development that has occurred in the last 30-years.
Irrigation is the major water user and increase of irrigation water consumption is the main
reason for the drying-up of the main river along the lower reaches [1]. Irrigation
management is the first step to a wise management of water resources in the Yellow
River basin. It needs to understand the spatial and temporal distribution of irrigation
water consumptions for exploring the way to saving water. However detail data of the
irrigation water consumption is usually unavailable and reliability of the statistic data is
also questionable in some periods.
Hydrological models have been widely used for water resources assessment, as well
as for irrigation water estimation. Water balance model is commonly used for this
purpose. Knox et al. [2] used a daily water balance model for estimating the net irrigation
water requirements for the main crops in England and Wales. Singh et al. [3] used
distributed modeling system, MIKE SHE for simulating the water balance of small
watershed with the objective of the irrigation development plan. Because the water
balance model couldn’t estimate evapotranspiration accurately without considering soil
water dynamics; however, the distributed hydrological model coupling with soil water
1
flux simulation can supply an appropriate tool for simulating soil-vegetation-atmosphere
transfer processes.
Figure 1. The Yellow River basin
In the present study, a 20-years (1981-2000) meteorological dataset in daily time
resolution was collected. Together with available geographic information related to the
topography, land uses and leaf-area-index, the irrigation water consumption in the
Yellow River basin was estimated using a grid-based distributed hydrological model,
which incorporated an irrigation scheme and a simple reservoir operation rule into the
geomorphology-based hydrological model (GBHM2) developed by Yang et al. [4].
Based on the simulation, the spatial and temporal variability of irrigation water
consumption is analyzed.
METHODOLOGY
Description of the distributed hydrological model
A distributed model, which incorporated an irrigation scheme and a simple reservoir
operation rule into the geomorphology-based hydrological model (GBHM2) developed
by Yang et al. [4,5], is employed for simulating irrigation water consumption in the
Yellow River basin in last 20-years. The model uses a grid-system with 10-km spatial
resolution, and it runs in an hourly time step.
Data Used in the Study
Topography The digital elevation data of 1-km resolution is obtained from the USGS
HYDRO1k data set which is available at: http://edcdaac.usgs.gov/gtopo30/hydro1k/.
2
Soil data The soil type is obtained from the Digital Soil Map of the World and Derived
Soil Properties [6]. It is developed in 5-minute resolution using the FAO-UNESCO soil
classification. The soil-water parameters used in the hydrological model are obtained
from a global soil dataset (Global Soil Task, 2000).
Meteorological data The daily meteorological data from 1981 to 2000 is collected from
China Meteorological Administration (CMA). The data are available at 108 stations
inside and close to the Yellow River basin (Fig.1). Meteorological parameters include
precipitation, maximum, minimum and mean air temperature, wind speed, relative
humidity, sunshine hours and pan evaporation. The hydrological required gridded input is
interpolated from the gauge data. Precipitation is interpolated using angular-distance
weighting method [7]. By the same way, wind speed, relative humidity and sunshine hour
are also interpolated into each 10-km grid. The temperatures (maximum, minimum and
mean) are interpolated using an elevation corrected angular-direction weighting method.
The daily potential evaporation is calculated using the wind speed, relative humidity,
sunshine duration and temperature [8] and calibrated using the pan evaporation.
Discharge The discharge data is collected from the “Hydrological Year Book” published
by Hydrological Bureau of the Ministry of Water Resources of China [9]. In this study, 6
gauges on the main river (see Fig. 1) are selected for analyzing the effect irrigation water
consumption on river discharges.
Shanshengong
Weir
Qintongxia
Dam
Longyanxia
Dam
Liujiaxia
Dam
Figure 2. Classification of land use and irrigation district
Land use and irrigation area Land use map is obtained from 1:250000 scale land use
map (Chinese Academy of Sciences). The land use map has been regrouped into 10
3
categories, including water body, urban area, bare land, forest, irrigated cropland, nonirrigated cropland, grassland, wetland, mixture of bare land and grassland, and ice. Area
fraction of each land cover type within a 10-km grid is calculated from the 1:250000
scale map. For each vegetation type, a monthly leaf-area-index (LAI) is calculated from
the monthly NDVI. A global dataset of monthly NDVI with 8-km resolution is obtained
from the DAAC of GSFC/NASA. This dataset is available since 1982. Moreover,
according the available data, irrigated farmland is classified as centralized irrigation
districts and distributed irrigation areas. The centralized irrigation district intakes water
from the common weir, which includes four major irrigation districts, the Qintongxia,
Hetao, Yimong and Longning in the upstream of the Huayuankou gauge. There are three
distributed irrigation areas, irrigation zone in upstream of the Toudaoguai gauge,
irrigation in Fenhe-Weihe River basin and irrigation zone between the Sanmenxia and
Huayuankou gauges in Henan province (see Fig. 2).
Crop and irrigation scheduling There are ten types of crops in the Yellow River basin.
Spring wheat is the domain crop in north-west part, winter wheat is the domain crop in
east-south part, maize is another common crop. Here the four main crops spring wheat,
spring maize, winter wheat and summer maize are considered in the study. Crops growth
period are obtained from literatures[10]. For each irrigation district, the crop calendar is
assigned according the statistic data. The irrigation includes a spring-irrigation (preplanting), a winter-irrigation (water-storing) and normal irrigation during the cropgrowing period. Water amounts for the spring-irrigation and the winter-irrigation are
relatively fixed. The water required during the growing period is determined by deficit of
the soil moisture which is simulated by the distributed hydrological model.
Approach to irrigation and reservoir operation
Reservoir operation The irrigation season is mainly during March to June, while
precipitation concentrates during July to October. Therefore the irrigation mainly relies
on 3174 reservoirs (total storage is 574  108 m 3 ), which stores water during the wet
season and supplies water during irrigation period [11]. Due to the lack of information for
most small reservoirs, here only 4 main reservoirs, Longyangxia, Liujiaxia, Qingtongxia
and Shanshengong are included. The reservoir operation is represented using a storage
function as follows
dS
(1)
 I (t )  Qdown (t )  Qirr (t )
dt
Where， S is reservoir storage (m3)， I is inflow discharge (m3/s)， Qdown is outflow
discharge from reservoir (m3/s)， Qirr is water intake by irrigation(m3/s).
In the case of no reservoir information, it is assumed that the irrigation area is proportion
to the reservoir storage in the same sub-basin. Then virtual reservoirs are assigned and
located to the sub-basin outlet according to the irrigation area distribution, and a
supposed storage is given to the reservoir.
Irrigation scheme An irrigation scheme (see Fig. 3) is used in the hydrological
simulation. During the growth period of crops, the lower and upper limitations of soil
moisture are determined according to the crop type. The water required during the
4
Soil
moisture
s
c  f
Irrigation
Water
growing period is determined by the deficit of soil moisture which is simulated by
distributed hydrological model. It is assumed that the water intake for centralized
irrigation districts is from fixed site with designed intake capacity, such as the
Qingtongxia irrigation district intakes water from the Qingtongxia reservoir by a capacity
of 600 m3/s. The Hetao irrigation district intakes water from the Shanshengong weir with
discharge of 700 m3/s. For the distributed irrigation areas water is taken from the virtual
reservoirs or the river of the same flow-interval. The discharge is in proportion to the
virtual reservoir storage or river flow. When reservoir storage is below the dead storage
or when river discharge is below the in-river discharge that is given arbitrary here, no
irrigation water can be taken. The irrigation time equals the water required divided by
intake discharge, and limited by maximum irrigation time. The irrigated water is
uniformly distributed over the irrigation area at the same time. The approach didn’t
consider the water loss in channel and waterway. So, the simulated irrigation water is net
irrigation water consumption.
Saturated soil moisture
Minimum soil moisture
Plant growth period
Planting
Harvest
Figure 3. The irrigation scheme
RESULTS
Based on the 20- years (1981-2000) simulation result, the simulated annual net irrigation
water consumption is 149.6  108m3 above the Huayuankou gauge. The spatial
distribution of net irrigation water consumption per unit area (see Fig. 4), in general,
reflects the spatial variability of climate. The highest irrigation water consumption per
unit area occurs in the semi-acrid region with very small annual precipitation, especially
in the Qingtongxia and Hetao irrigation districts. In the Weihe basin, net irrigation water
consumption per unit area is smaller than the mean value of 300 mm/yr, this is because of
its semi-humid climate. For the total net irrigation water consumption, high irrigation
water consumption concentrates mainly in the Qingtongxia, Hetao and Fenhe-Weihe
irrigation district. The details are given in table in Fig. 4.
Due to the lack of historical data of irrigation water uses, it is difficult to compare
the simulated values to the observed ones in each irrigation district. But some literatures
give the net irrigation water use, which is derived from difference of annual total intake
subtracting the return flow. The value for the Qingtongxia irrigation district is about
25.6  108m3, which is very close to the simulated value of 24.4  108m3. But for the total
annual net irrigation water consumption, the statistical data is 189.4  108m3 for the
upstream of Huayuankou gauge, which is about 40  108m3 larger than the simulated
value.
5
3
Simulated
Observed
8
60
50
40
30
20
10
0
Discharge(10 m )
Discharge(108m3)
Figure 4. Spatial distribution of net irrigation water consumption unit area
Lanzhou
Time(month)
70
60
50
40
30
20
10
0
Simulated
Observed
30
20
Toudaoguai
10
Time(month)
0
Discharge(108m3)
Discharge(108m3)
40
60
40
20
0
Simulated
Observed
Sanmenxia
Time(month)
1 2 3 4 5 6 7 8 9 10 11 12
Discharge(108m3)
Discharge(108m3)
1 2 3 4 5 6 7 8 9 10 11 12
80
Shizuishan
Time(month)
1 2 3 4 5 6 7 8 9 10 11 12
1 2 3 4 5 6 7 8 9 10 11 12
50
Simulated
Observed
60
50
40
30
20
10
0
Simulated
Observed
Longmen
Time(month)
1 2 3 4 5 6 7 8 9 10 11 12
100
80
Simulated
Observed
60
40
20
0
Huayuankou
Time(month)
1 2 3 4 5 6 7 8 9 10 11 12
Figure 5. Monthly river discharge at 6 gauges from upstream to downstream
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The difference between the simulated river discharge and observed river discharge
along the Yellow River can reflect the reasonability of irrigation water consumption
simulation. The comparison between simulated and observed 20-years monthly discharge
shows, good agreement is achieved in the lanzhou gauge, for it’s discharge controlled
mainly by two large reservoirs, the Liujiaxia and Longyangxia, and irrigation area is
small above the Lanzhou gauge. Some differences are found in the Huayuankou gauge,
the simulated is larger than the observed one, especially in the summer.
Figure 5 shows 20-years average of monthly discharge from hydrological simulation
and observation at 6 gauges from the upstream to downstream. For revealing regional
characteristics of the irrigation water consumptions, Table 1 gives the average annual
discharge and water consumption from 1981 to 2000 for the different sections from
upstream to downstream. At the Lanzhou gauge, simulated hydrograph agree well with
the observed one. At the Shuizuishan gauge, which locates below the Qingtongxia
irrigation district, the annual discharge error is below 1%, but hydrograph shows
discharge overestimated during irrigated period (March-July) and underestimated during
August-October. The Qingtonxia irrigation district, which is the main irrigation above the
Shuizuishan gauge, intakes a large amount of water and the drainage is also large. By the
statistics, the intake is 66.4  108m3/yr and drainage 40.9  108m3/yr, the net consumption
is 25.5  108m3/yr. That is the main reason for the difference between the simulated and
observed hydrographs at the Shuizuishan gauge. The most difference occurs at the
Toudaoguai gauge, which locates below the Inner Mongolia, the Hetao irrigation district
that is largest one in the Yellow River basin. Hydrograph shows discharge overestimated
mainly in May-July, the real water use is about 40  108m3 more than the simulated one.
The Inner Mongolia is the driest region in this basin, water loss in channel and ponds is
huge, and its drainage doesn’t return back to the Yellow River but into a lake and then
evaporated into atmosphere. Considering the channel efficiency of 0.6 at the present time,
the simulated water use is 118.5  108m3, which is very close to statistical average value
from 1998 to 2000. From the Toudaoguai to Huayuankou gauges, the discharge
difference between the gauges is relative close to the simulated net irrigation water
consumption in this region (see Table 1). Annual water transfer to out of the basin is
17.26  108m3, and industrial and domestic water consumption is 46.5  108m3 in the
Yellow river basin. Considering the water use for industry, urban use and transfer, the
underestimated irrigation water is about 40  108m3 considering.
Annual variability of the net irrigation water consumption has a close relationship
with the annual precipitation. The large amount of irrigation water consumption exists in
the dry years. In 1997, the annual precipitation is 338.3 mm, the simulated net irrigation
water consumption reaches 176.0  108m3/yr (24 mm/yr). However, irrigation water
consumption keeps nearly constant in the region between the Lanzhou and Toudaoguai
gauges. This implies that the region between the Lanzhou and Toudaoguai gauges is the
full irrigation-dependent area where the main water source is from irrigation.
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Table 1. Comparison irrigation water consumption in each sub-division（unit: 108m3）
Simulated discharge
Gauge
Lanzhou
Shizuishan
Toudaoguai
Longmen
Sanmenxia
Huayuankou
Observed discharge
In
gauge
Difference
between
gauges
In
gauge
Difference
between
gauges
395.69
383.87
343.26
386.55
496.16
553.34
-11.82
-40.61
43.29
109.61
57.18
384.89
386.05
267.1
317.51
404.54
448.5
1.16
-118.95
50.41
87.03
43.96
Simulated
irrigation
water use
Statistical irrigation
water use (1998-2000)
Surface
water
Ground
water
7.6
17.7
0.7
71.1
104.0
14.1
9.7
50.8
9.9
5.1
25.9
12.4
2.2
25.3
6.0
CONCLUSIONS
Using a 20-year (1981-2000) forcing data, together with available geographic
information related to the land surface, irrigation water consumption in the Yellow River
basin is estimated using a grid-based distributed hydrological model. The simulated
annual net irrigation water consumption is 149.6  108m3. Considering the water loss in
the channel and ponds in irrigation areas, the annual gross loss of river discharge for
irrigation is close to the statistical data. Comparison between simulated discharge and
observed discharge at 6 gauges from the upstream to downstream and comparison
between simulated and observed net irrigation water consumptions in the Qingtongxia
irrigation district, show that simulation of irrigation in this basin is reasonable, especially
good agreement is achieved for the centralized irrigation districts.
ACKNOWLEDGEMENT
This research was partially supported by the Core Research for Evolutional Science and
Technology (CREST) program of Japan Science and Technology Agency (JST). The
authors would like to appreciate their grant in aid on this research.
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